Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: Ray on January 22, 2007, 01:04:37 pm
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Well, it's happened! As a result of external hard drive storage becoming affordable, I decided to make a 'hard drive' duplicate of my CDs and DVDs. I bought 2 LaCie 500GB external drives (Big Disk). I spent hours transferring RAW & Tiff inages to them. One of the Big Disks I reserved for the images from my recent trip. I spent hours sorting the RAW files into appropriate folders.140GB of them. Fortunately, I didn't save any processed images to this hard drive, because it has now become corrupted. I seem to have lost access to all those 140GB of RAW images on the drive.
I've tried plugging the drive into the USB socket of other computers, but with the same result. The hard drive is recognised in 'hardware devices'. The driver appears to be working properly. But I can't find the drive in 'my computer', in 'windows explorer', or in Bridge.
I seem to have a drive in perfect working order which is invisible.
Geez! It's fortunate I've got this stuff backed up on DVD. The problem I now have is, this drive is still under warranty. Do I take it back to the store and hand over all my precious images, which might be copied by some unscrupulous employee who takes a fancy to my images and possibly sells them to some third party?
I've got no idea whether the images can be retrieved. However, if they are going to be retrieved, I'd like it to be me who does it.
Any advice would be appreciated.
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Those LaCie things are really consumer devices. I wouldn't put anything on them that my livelyhood depends on. Your best bet is to buy a multi-bay enclosure that has fans, and outfit it with drives from Seagate, Hitachi, or Western Digital. Connect it as a SATA drive if your computer supports SATA (individual drives need to be SATA as well), and you will have a more robust professional mechanism. SATA does not rely a bridgeboard to convert to Firewire/USB, as the data is piped directly into the HD. The type of RAID configuratipon or redundancy/back-up method is up to you. At least get the proper hardware.
Have you tried running a directory repair utility on your LaCie?
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Have you tried running a directory repair utility on your LaCie?
[a href=\"index.php?act=findpost&pid=97015\"][{POST_SNAPBACK}][/a]
Nope! But I'll investigate. Thanks for the advice.
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I've got no idea whether the images can be retrieved. However, if they are going to be retrieved, I'd like it to be me who does it.
Any advice would be appreciated.
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=97011\")
Go to [a href=\"http://www.r-tt.com/]http://www.r-tt.com/[/url] and look specifically at "R-Studio." I have found this program to be invaluable when bad (non-mechanical) things happen to good hard drives.
Ron
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Go to http://www.r-tt.com/ (http://www.r-tt.com/) and look specifically at "R-Studio." I have found this program to be invaluable when bad (non-mechanical) things happen to good hard drives.
Ron
[a href=\"index.php?act=findpost&pid=97161\"][{POST_SNAPBACK}][/a]
Thanks,
I'm downloading the demo version of R-Studio right now. I wrote in my original post 1.4Gb of data lost. In fact it's 140GB of RAW files that I can't access. It's the time lost in organising those images that makes me angry. The images were taken from DVDs I recorded in the field, day by day. I'd organised all images of 'sunrise at Angkor Wat' (for example) into one folder, and all images of Apsara bas reliefs into another folder and so on.
What amazes me is that I've never lost any images recorded (properly) to CD and DVD over a 10 year period, yet after just 3 or 4 weeks of duplicating images on an external hard drive, I've (maybe) lost 140GB.
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But I can't find the drive in 'my computer', in 'windows explorer', or in Bridge.[a href=\"index.php?act=findpost&pid=97011\"][{POST_SNAPBACK}][/a]
What about the disk manager? Maybe it just needs a drive letter, but somehow wound up without one?
What about disabling the device in Device Manager, and then re-enabling it?
I've had external drives disappear temporarily, only to come back again.
I'd try stuff like this before running any kind of rescue utility.
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What about the disk manager? Maybe it just needs a drive letter, but somehow wound up without one?
[a href=\"index.php?act=findpost&pid=97171\"][{POST_SNAPBACK}][/a]
John,
The drive is included in Device Manager and appears in Disk Management as an unallocated disk that has not been initialized. Inititializing the disk will apparently result in the loss of all data. The R-Studio data recovery program also recognises the disk, but doesn't recognise the sectors. A scan of the disk results in a series of 'fails' at each position.
Did I say it was a 300GB drive? It's a 500GB, or more precisely 465.8GB.
The question is, if I initialize the hard drive, which might result in my being able to use the drive again (although I'm not sure I even want to if this sort of thing can happen) is there then any possibility of recovering the data with a program like R-Studio?
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Hi Ray! You mentioned you've had this drive attached to several systems:
What system was the drive originally "stuffed" on? What O/S is it running? Do you know what filesystem is on the drive? Fat32 / NTFS / Other?
Regards - John
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Did I say it was a 300GB drive? It's a 500GB, or more precisely 465.8GB.
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=97183\")
That reminded me: have you enabled large disk support or 48-bit LBA in your BIOS?
More info (scroll down to 2. - Windows can only see 137GB of my 250GB IDE hard drive):
[a href=\"http://www.pcbuyerbeware.co.uk/HDDProblems.htm#common]http://www.pcbuyerbeware.co.uk/HDDProblems.htm#common[/url]
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Just a thought?
Spinrite has a good 'press' here is the site http://www.grc.com/spinrite.htm (http://www.grc.com/spinrite.htm)
HTH
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Hi Ray! You mentioned you've had this drive attached to several systems:
What system was the drive originally "stuffed" on? What O/S is it running? Do you know what filesystem is on the drive? Fat32 / NTFS / Other?
Regards - John
[a href=\"index.php?act=findpost&pid=97202\"][{POST_SNAPBACK}][/a]
Hi! John,
The drive came preformatted with the NTFS system and was plug & play for Windows 2000/XP. I'd used it in a couple of different locations and computers without any trouble until just recently. I was initially very impressed with it's ease of use. It can sit vertically on the desk top, takes up little space and is easily transportable. The only disadvantage I saw was the fact that the drive does not automatically switch off with the computer since it has its own power source. There has been more than one occasion when I forgot to switch the drive off, after turning the computer off, and have left the drive running all night. But that shouldn't harm it. Hard drives are designed to run all day or all night, aren't they.
The only thing I can think of that might have been the cause of this corruption of some necessary file (whatever file that is), is a removal of the drive from the system by inadvertantly pulling its power cord out. There's an icon at the bottom of my screen for 'safely removing hardware'. I presume there's some hazard if this facility is not used before removing a drive from a running system. I should add, however, there was no immediate problem after this occurrence. It was sometime later the disintegration began, first with Bridge refusing to respond, then with the drive not appearing in Windows Explorer, then briefly appearing with great difficulty after rebooting the computer several times, but not allowing me to copy the folders, then a warning message that Microsoft could not copy file M$/** whatever (I should have written it down but I was panicking ), and then finally no directory or folders.
I have another of these 500GB LaCie BigDisks holding about 400GB of data. The data is also on DVD, but once again, it's the time spent oranizing the images that would be lost if something eventually happens to this drive.
The drive was originally stuffed on my XP64 edition OS.
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That reminded me: have you enabled large disk support or 48-bit LBA in your BIOS?
More info (scroll down to 2. - Windows can only see 137GB of my 250GB IDE hard drive):
http://www.pcbuyerbeware.co.uk/HDDProblems.htm#common (http://www.pcbuyerbeware.co.uk/HDDProblems.htm#common)
[a href=\"index.php?act=findpost&pid=97233\"][{POST_SNAPBACK}][/a]
I must have because I've been using 2x200GB internal drives initially installed when this XP64 bit system was new and I've been using the LaCie 500GB BigDisk for several days without problem.
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Thanks for the info Ray! Let me do a bit of checking - you should be able to recover the drive, assuming we're not dealing with a physical problem.
http://www.microsoft.com/technet/prodtechn.../c28621675.mspx (http://www.microsoft.com/technet/prodtechnol/winxppro/reskit/c28621675.mspx)
You *should* use the remove hardware applet, especially for block (storage) devices. NTFS is a true journalled filesystem - so an interrupted write should not corrupt the filesystem, using the remove hardware ensures that all pending writes have been performed . .
take care - John
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Let me do a bit of checking - you should be able to recover the drive, assuming we're not dealing with a physical problem.
[a href=\"index.php?act=findpost&pid=97244\"][{POST_SNAPBACK}][/a]
Thanks. In the meantime I should not attempt to initialize the drive, right?
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Ray: I seemingly simple question, that I have yet to find an answer for
My gut tells me, yes it *is* destructive - but Microsoft's terminology is often at odd's with others.
Try this:
Open a command prompt: Start Button | Run | type "cmd" (without the quotes)
In the "dos box" type "diskpart" (again without the quotes). In the following, I'm putting my CF card "online". In your case use whatever disk # corresponds to your situation . . .
[span style=\'font-size:8pt;line-height:100%\']Microsoft DiskPart version 6.0.6000
Copyright © 1999-2007 Microsoft Corporation.
On computer: OFFICE
DISKPART> list disk
Disk ### Status Size Free Dyn Gpt
-------- ---------- ------- ------- --- ---
Disk 0 Online 202 GB 835 KB
Disk 1 Online 977 MB 0 B
Disk 2 No Media 0 B 0 B
Disk 3 No Media 0 B 0 B
DISKPART> select disk 1
Disk 1 is now the selected disk.
DISKPART> online
DiskPart successfully onlined the selected disk's pack.
DISKPART>exit[/span]
close the windows, then re-open disk management (Start | Run | "diskmgmt.msc"). Let us know what you see . . .
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Those LaCie things are really consumer devices.… At least get the proper hardware.
[a href=\"index.php?act=findpost&pid=97015\"][{POST_SNAPBACK}][/a]
Or better yet learn who makes the hardware.
LaCie does NOT make hard drives. Inside of a LaCie enclosure you will find hard drives from the various manufacturers, IBM/Hitachi, WD or Seagate/Maxtor.
How these drives are connected doesn't matter when it comes to reliability. So advice on using a SATA card vs. USB or whatever is really a topic for another thread.
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Ray: I seemingly simple question, that I have yet to find an answer for
My gut tells me, yes it *is* destructive - but Microsoft's terminology is often at odd's with others.
Try this:
Open a command prompt: Start Button | Run | type "cmd" (without the quotes)
In the "dos box" type "diskpart" (again without the quotes). In the following, I'm putting my CF card "online". In your case use whatever disk # corresponds to your situation . . .
[span style=\'font-size:8pt;line-height:100%\']Microsoft DiskPart version 6.0.6000
Copyright © 1999-2007 Microsoft Corporation.
On computer: OFFICE
DISKPART> list disk
Disk ### Status Size Free Dyn Gpt
-------- ---------- ------- ------- --- ---
Disk 0 Online 202 GB 835 KB
Disk 1 Online 977 MB 0 B
Disk 2 No Media 0 B 0 B
Disk 3 No Media 0 B 0 B
DISKPART> select disk 1
Disk 1 is now the selected disk.
DISKPART> online
DiskPart successfully onlined the selected disk's pack.
DISKPART>exit[/span]
close the windows, then re-open disk management (Start | Run | "diskmgmt.msc"). Let us know what you see . . .
[a href=\"index.php?act=findpost&pid=97248\"][{POST_SNAPBACK}][/a]
John,
I also get a list of disks from 0 to 3 when I follow this procedure. However, the LaCie BigDisk is number 4, as shown under disk management, unknown and unallocated. It doesn't appear on this DOS page.
I've sent an email to LaCie technical support, mainly to ask them how this sort of thing could have happened. I'm reluctant to continue using external drives without identifying the cause of this apparent directory destruction. I mean, was it something I did?
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Or better yet learn who makes the hardware.
LaCie does NOT make hard drives. Inside of a LaCie enclosure you will find hard drives from the various manufacturers, IBM/Hitachi, WD or Seagate/Maxtor.
How these drives are connected doesn't matter when it comes to reliability. So advice on using a SATA card vs. USB or whatever is really a topic for another thread.
[a href=\"index.php?act=findpost&pid=97249\"][{POST_SNAPBACK}][/a]
Most LaCies use Maxtors, and Maxtor has had one of the worst ratings up until Seagate bought them. But with LaCie merely buying components from the cheapest vendor, it only goes to follow that the bridgeboard reliability needs to be considered as well. Their products are designed, assembled, and marketed to fit into the mass marketer realm of things. IOW, the look and color of the case and the cool looking knobs seems to take precendence over how it really works. My multi-bay tower is made out of stamped metal, not much design aesthetic, but it is only designed to house drives in a fan cooled enclosure. If I wanted to use ATA drives, then I can choose whatever vendors bridgeboard I want with regard soley to that vendors reliability.
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Have you taken the drive out of the enclosure and tried to access it connected directly? Sometimes the interface in the enclosure fails as well.
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Have you taken the drive out of the enclosure and tried to access it connected directly? Sometimes the interface in the enclosure fails as well.
[a href=\"index.php?act=findpost&pid=97680\"][{POST_SNAPBACK}][/a]
No, I haven't tried that. The drive is still under warranty. I've already started re-transferring the lost data, from the original DVDs and a pocket hard drive, to a cleared internal drive. Untill I try initializing the LaCie drive in 'disk management', I won't know if the hardware is faulty. I've been holding off doing this, waiting for a reply from LaCie Technical Support, hopefully with some helpfull suggestions.
The issue now for me is, if the drive initializes okay and is useable again, should I be using it without understanding what caused this corruption of the directory? Once bitten, twice shy.
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Hard disks have a finite failure rate, even if its one in a 100 million, one will die somewhere. Its just bad luck its you !
If it has had a problem once, chances are that it will do it again. The controllers inside will map out bad sectors but won't protect you from more sectors going bad.
Ian
http://www.colourperfect.co.uk (http://www.colourperfect.co.uk)
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Hard disks have a finite failure rate, even if its one in a 100 million, one will die somewhere. Its just bad luck its you !
If it has had a problem once, chances are that it will do it again. The controllers inside will map out bad sectors but won't protect you from more sectors going bad.
Ian
http://www.colourperfect.co.uk (http://www.colourperfect.co.uk)
[a href=\"index.php?act=findpost&pid=97700\"][{POST_SNAPBACK}][/a]
I'll take it back to the store and see if I can get it replaced. I don't even want to try to get it working again .
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I'll take it back to the store and see if I can get it replaced. I don't even want to try to get it working again .
[a href=\"index.php?act=findpost&pid=97721\"][{POST_SNAPBACK}][/a]
I got the following reply from LaCie, at last. They must be snowed under with queries and complaints, perhaps from a backlog due to the holiday season.
Hi Raymond,
Directory corruption can be either software or hardware related. To
eliminate a hardware problem we suggest that you perform a full NTFS format.
If the format does not complete then the problem is most likely unreadable
sectors on the drive. In this case the drive will need to be
repaired/replaced.
Best Regards,
LaCie Australia - Support Team
I was sort of hoping they might provide a suggestion as to how to recover the data. I gather from this reply that the fault could be either hardware or software. If the drive initializes successfully, then the fault is software based. If it doesn't, then it's hardware based.
I've just tried initializing the drive. The operation cannot be completed. I have a faulty drive that's been used for less than a month. I'm normally lucky. At least I have been with all my CD/DVD back-ups.
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Did you ask them what device they recommend you use as a back up to your backup?
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Did you ask them what device they recommend you use as a back up to your backup?
[a href=\"index.php?act=findpost&pid=98000\"][{POST_SNAPBACK}][/a]
No, of course I didn't. I didn't want to appear sarcastic. But I am seriously considering arranging my 'image organisation' into 4.3GB folders, so I can do a DVD back-up of the organisation easily.
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http://www.secondcopy.com/ (http://www.secondcopy.com/) - spans disks if needed, highly recommended
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http://www.secondcopy.com/ (http://www.secondcopy.com/) - spans disks if needed, highly recommended
[a href=\"index.php?act=findpost&pid=98009\"][{POST_SNAPBACK}][/a]
It's not clear to me if this is what I want. If I have 100GB of organised images, for example, will this program record my images onto (approx) 25 consecutive DVDs?
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A more polite (and to the point) question might be "how can I trust this device for future work knowing that it has already failed once?"
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A more polite (and to the point) question might be "how can I trust this device for future work knowing that it has already failed once?"
[a href=\"index.php?act=findpost&pid=98019\"][{POST_SNAPBACK}][/a]
I think an unanswerable question. No employee of LaCie is going to write, "You can't". I just hope they replace it instead of repairing it.
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It's not clear to me if this is what I want. If I have 100GB of organised images, for example, will this program record my images onto (approx) 25 consecutive DVDs?
[a href=\"index.php?act=findpost&pid=98015\"][{POST_SNAPBACK}][/a]
Yes!
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Yes!
[a href=\"index.php?act=findpost&pid=98137\"][{POST_SNAPBACK}][/a]
Hmm! The question I am really asking is, will 'Second Copy' organize a series of folders into 4.35Gb packages for easy recording with a burning program like Nero. It's not at all clear reading the FAQ.
This I think is the main objection that most people have to backing up huge amounts of data on DVD. If you want to efficiently fill up each disc with 4.3 to 4.4Gb of images, it requires a lot re-organising and breaking-up of folders; a lot of time-consuming preparation for each disc burned.
If 'Second Copy' can't do this, then perhaps the safest thing to do is make the initial organization of one's images in 4.3GB packages, say "Disc 1 - Angkor Wat sunrises - Apsara bas reliefs", "Disc 2 - Apsara Bas Reliefs (cont:-) - Bayon", "Disc 3 - Bayon (cont:-) - Ta Prohm etc etc".
With such a system, at some future date when 25Gb Blu-ray discs have become affordable (or competitive in price), and provided the data on the hard drive(s) have not become corrupted, one could simply drag and drop 5 of these DVD size folders into the burning application, at least almost filling up each Blu-ray disc.
Does this all sound too cumbersome? Is there a simpler way that has escaped me?
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Ray:
2nd copy works very similarly to xCopy in that it is capable of backuping up an entire folder hierarchy to another device - be that an FTP store (I use this as a secondary backup for source code), Network, or Optical Media.
There is built in "profile" capability that will update re-writable stores, can also be scheduled.
The thing I like about it is:
1) It will span multiple disks
2) The exact same profiles can be sent to different media if desired, handy if upgrading to a larger drive or transferring between machines across a network
From 2nd Copies' FAQ:
http://www.secondcopy.com/support.html#Q_CDRW (http://www.secondcopy.com/support.html#Q_CDRW)
[span style=\'font-size:8pt;line-height:100%\']Does Second Copy work with CD-R/CD-RW drives?
Yes. Second Copy works with CD Recordable/ReWritable drives (CD-R/CD-RW) if a proper device driver is installed and configured with your drive. The driver should make the CDRW behave like a large floppy disk.
Nero InCD (part of Nero 6 or later) and Roxio DirectCD (part of Easy Media Creator) are two such products that work with various CD-R/CD-RW drives and makes them look like large floppy disks. Check with your CD-R/CD-RW documentation.
One simple test to see if Second Copy will work with a CD-R/CD-RW drive is to see if you can copy files from your hard disk to the CD-R/CD-R/CD-RW drive using Windows Explorer. If Windows Explorer can copy files to the drive Second Copy can too.
Windows XP: Window XP is included with a "lite" version of Adaptec/Roxio's Easy CD and it does not make the CD-R/RW look like a hard disk. You will need to install a packet writing software such as Roxio's DirectCD for Windows XP. DirectCD is included with Easy Media Creator for Windows XP. DirectCD allows your CD-R/RW drive to appear just like any other drive volume. In other words, your CD-R/RW drive handles files just like a hard disk or floppy disk. Once you have Direct CD installed on your system, you can drag and drop files to the CD-R/RW as well as use Second Copy 2000 to backup your files to the CD-R/RW drives. [/span]
hth - John
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Ray:
2nd copy works very similarly to xCopy in that it is capable of backuping up an entire folder hierarchy to another device - be that an FTP store (I use this as a secondary backup for source code), Network, or Optical Media.
There is built in "profile" capability that will update re-writable stores, can also be scheduled.
The thing I like about it is:
1) It will span multiple disks
2) The exact same profiles can be sent to different media if desired, handy if upgrading to a larger drive or transferring between machines across a network
From 2nd Copies' FAQ:
http://www.secondcopy.com/support.html#Q_CDRW (http://www.secondcopy.com/support.html#Q_CDRW)
[span style=\'font-size:8pt;line-height:100%\']Does Second Copy work with CD-R/CD-RW drives?
Yes. Second Copy works with CD Recordable/ReWritable drives (CD-R/CD-RW) if a proper device driver is installed and configured with your drive. The driver should make the CDRW behave like a large floppy disk.
Nero InCD (part of Nero 6 or later) and Roxio DirectCD (part of Easy Media Creator) are two such products that work with various CD-R/CD-RW drives and makes them look like large floppy disks. Check with your CD-R/CD-RW documentation.
One simple test to see if Second Copy will work with a CD-R/CD-RW drive is to see if you can copy files from your hard disk to the CD-R/CD-R/CD-RW drive using Windows Explorer. If Windows Explorer can copy files to the drive Second Copy can too.
Windows XP: Window XP is included with a "lite" version of Adaptec/Roxio's Easy CD and it does not make the CD-R/RW look like a hard disk. You will need to install a packet writing software such as Roxio's DirectCD for Windows XP. DirectCD is included with Easy Media Creator for Windows XP. DirectCD allows your CD-R/RW drive to appear just like any other drive volume. In other words, your CD-R/RW drive handles files just like a hard disk or floppy disk. Once you have Direct CD installed on your system, you can drag and drop files to the CD-R/RW as well as use Second Copy 2000 to backup your files to the CD-R/RW drives. [/span]
hth - John
[a href=\"index.php?act=findpost&pid=98224\"][{POST_SNAPBACK}][/a]
Yes, I read this, John, but I have no intention of using CDs for backing up images. I'm not sure that DVDs lend themselves well to multisession writing. At least there's a warning with Nero that only the last session might be readable in other drives. I've got a stack of failed DVD recordings accumulated over the past few years. I haven't had any failed recordings yet using Nero and my current Pioneer burner.
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Maybe I'm missing something, but hard drives are known to fail and as such are not recomended as a single-source for back up. This is old news and has been discussed ad-nauseum. Why try to re-invent the wheel? Most folks simply back up an to exact duplicate hard drive. If one fails, you can replace it or reformat it and re-copy the data from the second back-up to it -- presto, done, no data permanently lost and a *lot* faster and a *lot* more convenient than DVD's. Heck, 500G SATA drives are now under $200 -- about 40 cents/Gig which is *cheaper* than quality archival (gold) DVDs. You can buy external cases to hold them for around $50 and still remain under the cost of the archival DVD's. Seems to me to be a no-brainer...
Good luck regardless,
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Yes, I read this, John, but I have no intention of using CDs for backing up images. I'm not sure that DVDs lend themselves well to multisession writing. At least there's a warning with Nero that only the last session might be readable in other drives. I've got a stack of failed DVD recordings accumulated over the past few years. I haven't had any failed recordings yet using Nero and my current Pioneer burner.
[a href=\"index.php?act=findpost&pid=98299\"][{POST_SNAPBACK}][/a]
The same warning applies to CD-ROMs and is just as (in)valid. All modern DVD players can read multi-session DVDs. Nevertheless, I'd be on the safe side with backups and not use multi-session recording since I'm paranoid.
But I also would recommend sticking with redundant HDD backups. I don't know how many DVDs you have to backkup, but if its anything beyond, say, 20, I'd go for HDD from purely a convenience POV.
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Maybe I'm missing something, but hard drives are known to fail and as such are not recomended as a single-source for back up. This is old news and has been discussed ad-nauseum. Why try to re-invent the wheel? Most folks simply back up an to exact duplicate hard drive. If one fails, you can replace it or reformat it and re-copy the data from the second back-up to it -- presto, done, no data permanently lost and a *lot* faster and a *lot* more convenient than DVD's. Heck, 500G SATA drives are now under $200 -- about 40 cents/Gig which is *cheaper* than quality archival (gold) DVDs. You can buy external cases to hold them for around $50 and still remain under the cost of the archival DVD's. Seems to me to be a no-brainer...
Good luck regardless,
[a href=\"index.php?act=findpost&pid=98310\"][{POST_SNAPBACK}][/a]
Jack,
You have missed something.
(1) The external 500GB hard drive was bought for the purpose of organising the RAW images from my last trip. I considered it more efficient to complete the organisation before making a duplicate back-up, which involved deleting duplicate images and duds and grouping images in the same category under a single heading (folder), copied from across a large number of DVDs. This process was carried out over a couple of weeks using different computers in different locations. I did not think it was necessary to carry two rather heavy external drives around.
(2) It was my intention to clear an internal 200Gb drive on my Win XP 64 system to make a duplicate of the organization, once complete. However, considering the chances very remote of a new hard drive going faulty within the first few weeks of use, I didn't treat this with the urgency I should have.
(3) I have a preference for DVDs as maintenance-free archival storage because I have never lost any images this way in the last 12 years of use. I have no 12 year old hard drives that are still working, but I have dozens of 12 year old CDs that perform better and faster than they did when they were first burned. Example, my first Kodak Photo-CD images took 2 minutes to open. Those same images now open in just 10 seconds.
(4) In Australia, blank DVDs bought in spindles of 50 or so, are far cheaper per gig than hard drive storage, whether internal or external.
(5) Example: A cloth bound wallet with a zip around 3 sides, holding 96 discs in plastic sleeves, costs about A$5 (US$ 3.50). 96 discs are not quite enough to hold 500GB (actually 486GB) of data, but are pretty close. A spindle of 50 DVDs range from A$20 to A$35. Using the more expensive brand, $70 worth of blank DVDs are suffient to back up almost this entire LaCie external drive. The wallet that holds them all has about the same physical dimensions as the LaCie BigDisk and would be no heavier when full of discs; probably lighter.
Cost comparison:- A$75 including wallet (call it $100); LaCie BigDisk A$465. I bought the BigDisk because it seemed at the time substantailly cheaper than competing Maxtor and Seagate brands.
Hope I have filled in what you might have missed, Jack.
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Ah -- I missed the part you wanted to edit your entire portfolio before backing it up... I would think it more prudent to make a duplicate copy of everything, then go back and edit a working copy -- but I guess everybody has different ideas on workflow.
Two points offered only FWIW... My IT guru tells me that hard drive failure is more apt to occur in the first 10 hours of run on a new drive than the next 10,000, so it's always a good idea to stress drives a bit before using them for critical data (he has a program he runs that exercises the drives overnight). Also, I understand regular DVD's (the $30 per spindle of 50 type) are not considered archival as gold DVD's are, which run about $3.00 each and the number I used for my cost comparison. I think it has to do with the fact DVD/CD can delaminate and moisture can then enter and oxidise the aluminum foil rendering it unreadable, coupled with the cheaper dye layer being able to run if exposed to excessive heat which also will corrupt the read. The way I understand it, archival DVD/CD use gold foil because it doesn't corrode if the edge separates and use harder dyes that won't run at environmentally high heats.
All offered FWIW only and again, best wishes for getting everything restored!
Cheers,
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They say that misery loves company so just as a note/warning to those using these large capacity LaCie drives (I have a pile of them):
The way LaCie create these large drives is by installing 2 or more smaller drives and runs them as RAID 0 - stripping data over the drives so that they appear to be the size of the sum of the drive sizes. i.e. 2x250GB drives appear to be a 500Gb drive. Unfortunately this has a serious side effect in that the chances of a drive or controller failure hurting your data is actually much worse (2x ++) than a single high capacity drive would since either drive failing, or the controller, will leave you with lost data.
I had two of the LaCie BigDisk 500Gb drives fail. As it happens I live very close to the LaCie headquarters in Oregon so I was able to get both drives replaced under warranty in person. In my case, all data was lost when the drives failed but luckily they were at different times and were my backup mirror drives. One drive failed within a few days, the other was probably 6 months old. You can probably find posts on the internet about these drives & reliability. They are competitively priced because they are using commodity drives.
I'm sure that for every customer like me (or Ray!) there are probably 1000's who never have a failure. If that's you, great! The only thing I would suggest is that you have a good backup strategy just in case. I managed to have 50% failure rate with my 4 drives which isn't great statistics however you calculate them. I finally ended up investing in a 3Gb RAID 5 array & controller using the best SATA disks can buy at this time. With the benefit of hindsight I'd have gone this route from the very beginning.
On the bright side, LaCie were very accomodating and replaced my drives without question. I still use them but I don't trust them for critical content. Twice bitten etc etc ...
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I think it has to do with the fact DVD/CD can delaminate and moisture can then enter and oxidise the aluminum foil rendering it unreadable, coupled with the cheaper dye layer being able to run if exposed to excessive heat which also will corrupt the read.
I've seen this. The neat thing is that it tends to get worse as you use the DVD. So if you see your DVD start to delaminate you want to copy that data soon because it will only get worse.
Had an entire spindle of optorite disks do this. You could see that some started to fail on the initial burn. (around the center spindle.)
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Had an entire spindle of optorite disks do this.
Yep... It's why I don't use DVD for back-up. I think the best solution is RAID 1-1 for historical images and RAID 1-1-1 for working images with the last mirror stored offsite in a secure place (brought in to back up 1x per month or after any big job). It's virtually a bomb proof back-up solution and at the current price of 40 cents per Gig on 500 G SATA drives, it's cheap even for the working image files IMO. Plus you can re-use the working drive for every pair of copy drives you fill, making your "true" storage cost 80 cents per Gig -- and only getting cheaper...
My .02 only,
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They say that misery loves company so just as a note/warning to those using these large capacity LaCie drives (I have a pile of them):
The way LaCie create these large drives is by installing 2 or more smaller drives and runs them as RAID 0 - stripping data over the drives so that they appear to be the size of the sum of the drive sizes. i.e. 2x250GB drives appear to be a 500Gb drive. Unfortunately this has a serious side effect in that the chances of a drive or controller failure hurting your data is actually much worse (2x ++) than a single high capacity drive would since either drive failing, or the controller, will leave you with lost data.
I had two of the LaCie BigDisk 500Gb drives fail. As it happens I live very close to the LaCie headquarters in Oregon so I was able to get both drives replaced under warranty in person. In my case, all data was lost when the drives failed but luckily they were at different times and were my backup mirror drives. One drive failed within a few days, the other was probably 6 months old. You can probably find posts on the internet about these drives & reliability. They are competitively priced because they are using commodity drives.
I'm sure that for every customer like me (or Ray!) there are probably 1000's who never have a failure. If that's you, great! The only thing I would suggest is that you have a good backup strategy just in case. I managed to have 50% failure rate with my 4 drives which isn't great statistics however you calculate them. I finally ended up investing in a 3Gb RAID 5 array & controller using the best SATA disks can buy at this time. With the benefit of hindsight I'd have gone this route from the very beginning.
On the bright side, LaCie were very accomodating and replaced my drives without question. I still use them but I don't trust them for critical content. Twice bitten etc etc ...
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=98416\")
LaCie BigDisks seem to get really poor customer ratings on several sites. Amazon show many people complaining. The same on Newegg: [a href=\"http://www.newegg.com/Product/CustratingReview.asp?item=N82E16822154070]http://www.newegg.com/Product/CustratingRe...N82E16822154070[/url]
You may do better and cheaper with a third-party enclosure and a good hard drive.
As for RAID 0, as an IT person, I'll say that it's a totally ridiculous idea to use RAID 0 for anything but transient data that requires high performance reads/writes. I would not use other RAID setups for a back-up either, but rather duplicate onto separate drives. RAID 1 or 5 setup does protect you from a mechanical failure of one of the drives, however it does not protect you from user error (opps, I just deleted that folder/reformatted/etc..), does not protect you from a virus, does not allow to have drives in separate locations, does not protect you from RAID controller failure (and if it fails - good luck recovering your data except maybe for a RAID 1 setup.)
--Misha
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I've seen this. The neat thing is that it tends to get worse as you use the DVD. So if you see your DVD start to delaminate you want to copy that data soon because it will only get worse.
Had an entire spindle of optorite disks do this. You could see that some started to fail on the initial burn. (around the center spindle.)
[a href=\"index.php?act=findpost&pid=98417\"][{POST_SNAPBACK}][/a]
I live in a humind, tropical environment. I've never had experience of this. I'm still convinced some of you guys are buying substandard rejects at either a bargain price, or a price that gives the seller a huge profit margin.
It's the responsibility of the consumer to complain like hell. If I ever bought some CDs or DVDs that started delaminating, I'd complain like hell. But if some of you guys are buying nondescript discs from nondescript suppliers who vanish by night, then I guess you have no recourse. Who do you complain to? Luminous Landscape?
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Two points offered only FWIW... My IT guru tells me that hard drive failure is more apt to occur in the first 10 hours of run on a new drive than the next 10,000, so it's always a good idea to stress drives a bit before using them for critical data (he has a program he runs that exercises the drives overnight).
Jack,
I used this drive for many more than 10 hours over a 3 week period, and even occasionally left it on all night. It doesn't switch off automatically with the computer.
Also, I understand regular DVD's (the $30 per spindle of 50 type) are not considered archival as gold DVD's are, which run about $3.00 each and the number I used for my cost comparison. I think it has to do with the fact DVD/CD can delaminate and moisture can then enter and oxidise the aluminum foil rendering it unreadable, coupled with the cheaper dye layer being able to run if exposed to excessive heat which also will corrupt the read.
I have no CDs or DVDs, ranging from the cheapest I could buy (from a reputable store) to Kodak Gold, that have delaminated or given any trouble at all that wasn't related to a substandard CD-ROM drive.
If I was in the business of producing recordable CD/DVDs and the public became aware of a number of failures in the medium, that were highly exaggertated by the press, I would certainly think up some bullshit about increased protective layers or gold plating, and charge a premium for it. Wouldn't you? This is all politics... sorry! politics and business.
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It's the responsibility of the consumer to complain like hell.
It isn't an isolated problem, but endemic; it's simply the nature of the beast. And from what I undrestand, it usually takes time for the delamination to occur -- I've heard 7 years is considered modal life-span for non-archival DVD (compared to 25 years for archival gold). What is the "warranty" period on the DVD's you are buying? Regardless of what it is, what do they do if a disc fails during the warranty period? Probably replace the disc, and not likely the data on it. So when it happens, for sure complain away -- but I doubt that will result in your lost data being replaced.
Cheers,
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It isn't an isolated problem, but endemic; it's simply the nature of the beast. And from what I undrestand, it usually takes time for the delamination to occur -- I've heard 7 years is considered modal life-span for non-archival DVD (compared to 25 years for archival gold). What is the "warranty" period on the DVD's you are buying? Regardless of what it is, what do they do if a disc fails during the warranty period? Probably replace the disc, and not likely the data on it. So when it happens, for sure complain away -- but I doubt that will result in your lost data being replaced.
Cheers,
[a href=\"index.php?act=findpost&pid=98428\"][{POST_SNAPBACK}][/a]
You're not suggesting, Jack, are you that one day I might wake up and a 140GB of DVD storage has become corrupted. I expect if I'm still contributing in 10 years time to this site, I might start a new thread, "Hey, I've come acrross a 22 year old CD that's unreadable. I've tried every drive and every data recovery program but to no avail. I guess Jack Flesher was right after all. Serves me right!"
I should add that in 10 years time it's highly unlikely I shall have valued images that are only archived on CD. In 10 years time they will probably all have been transferred to the successor of Blu-ray. But it will certainly be interesting to see just how long these early CD recordings last.
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I just had further thoughts on this issue, but my internet connection was severed at the time I posted and I lost my post.
But, not to be deterred, here it is.
I'm deeply worried about accountability in America. Last night I watched a program on SBS in Australia (Special Broadcasting Services which is usually hard hitting), which outlined the total fiasco with regard to the Iraqi reconstruction fund. Here you have a case of billions of dollars being misspent, misappropriated and plain stolen.
There appears to be an enormous rip-off that has taken place.
When I see reports on this site of CDs and DVDs suffering from 'bit rot', what am I to think? I've not experienced it in Australia. Is America the recipient of all scams, I wonder.
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I live in a humind, tropical environment.
Well, that certainly increases the risk of HDD (hard disk drive) failure.
I've stated my opinions regarding backups before, and I'll only reiterate one point:
If anyone chooses to go with HDD-based backups, keep in mind that when one of your HDDs fail, you'll have a time period when the duplicate is at risk without redundancy, unless you have triplicates instead of duplicates.
As an IT professional, such temporary lack of redundancy makes me more than a bit queasy.
So if someone is going for purely HDD-based backups, use triplicates, or at the very least make sure that you have the replacement drive(s) ready for data transfer at the time of failure, not later. Sod's Law implies that the second drive will fail within short time of the first, especially if you don't have a backup of the second, too.
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Raid 0 2-drive arrays do not double the the risk of failure, they square it. So using them for archival purposes is dubious at best. RAID 5 is slower, but the stability and fail-safeness are well worth the hassle of waiting a few extra seconds for a file to save to the array.
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Raid 0 2-drive arrays do not double the the risk of failure, they square it. So using them for archival purposes is dubious at best. RAID 5 is slower, but the stability and fail-safeness are well worth the hassle of waiting a few extra seconds for a file to save to the array.
[a href=\"index.php?act=findpost&pid=98526\"][{POST_SNAPBACK}][/a]
Jonathan, with all due respect, the risk of failure for a 2-disk RAID 0 is double (almost), not square. (if by risk you mean probability if failure)
Assume x is probability of failure of one disk in the next year.
Then the probability of a disk working properly for a year is (1-x). The probability of two disks working properly for a year then would be (1-x)(1-x).
Then the probablility of failure of 2-disk RAID 0 is:
1-(1-x)(1-x) = 1 - 1 + 2x - xx = 2x - xx. As the value of x is a small value less then 1, the 2x in this formula is a dominating factor and xx is of a smaller order of magnitude.
So, if x = 0.05 (i.e a probability of failure is 5%), then the probability of failure of RAID 0 is 2x - xx = 0.10 - 0.0025 = 0.0975 (i.e just below 10%)
--Misha
PS. As for your point regarding RAID 5, agree about reliability and stability, but look at my post a few posts above regarding general risks involved in relying on RAID setups. RAID has its benefits but I do not see them in the back-up/offline storage domain.
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Well, that certainly increases the risk of HDD (hard disk drive) failure.
I've stated my opinions regarding backups before, and I'll only reiterate one point:
If anyone chooses to go with HDD-based backups, keep in mind that when one of your HDDs fail, you'll have a time period when the duplicate is at risk without redundancy, unless you have triplicates instead of duplicates.
As an IT professional, such temporary lack of redundancy makes me more than a bit queasy.
So if someone is going for purely HDD-based backups, use triplicates, or at the very least make sure that you have the replacement drive(s) ready for data transfer at the time of failure, not later. Sod's Law implies that the second drive will fail within short time of the first, especially if you don't have a backup of the second, too.
[a href=\"index.php?act=findpost&pid=98479\"][{POST_SNAPBACK}][/a]
This is not unique to HDDs, or to any backup media. Quite the contrary, actually. I'd argue this issue is even more prevalent for DVDs/CD-ROMs, as people tend to burn a DVD, tug it in a pouch and forget it. If they need that backup years later they might see bitrot has taken its toll - this might be the case even with redundant DVD backups.
With HDDs you are generally copying data to the same HDD, thus ensuring its integrity every time you do so. How many people backing up on DVDs check their integrity periodically?
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So, if x = 0.05 (i.e a probability of failure is 5%), then the probability of failure of RAID 0 is 2x - xx = 0.10 - 0.0025 = 0.0975 (i.e just below 10%)
--Misha
Sorry, not so, your formula is wrong. The correct formula is (1-x)^(number of drives). Let's say a drive has a 5% probability of failure in a given year. That means it has a 95% chance of operating failure-free. If you have 2 drives in a RAID0 array, the probability of the array NOT experiencing a drive failure in the next year is (.95 * .95), or 90.25%, which means that your odds of 100% data loss have jumped from 5% to 9.75%. Adding a third drive increases your failure odds to 14.26%, and so on.
On the other hand, in a RAID5 configuration, the likelihood of total data loss due to drive failure is x ^ (# of simultaneous failed drives required to fail the array, usually 2) * (repair time factor). The repair time factor is the time interval between a drive fault and the replacement of the defective drive and the rebuild of the array. If that time interval is one day, then your factor would be 1/365. If it wasa year, it would be 1. Given an X of 0.05, a 4-drive RAID0 array would have an 18.55% chance of total data loss in one year, while a 4-drive RAID5 array has a 0.25% chance of failure, if you don't fix it. If you repair and rebuild within 24 hours of a drive failure, the array failure probability (at least due to disk failure) drops to .000685%.
Of course, there are other risk factors involved, like controller failure, human error, viruses, fire, flood, power surges, etc that raise the probability of data loss considerably. But if you back up your data to two separate RAID5 devices that are not in the same building, on different branch circuits, etc. your data is about as safe as you can get it, but is still easily accessible.
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Sorry, not so, your formula is wrong. The correct formula is (1-x)^(number of drives). Let's say a drive has a 5% probability of failure in a given year. That means it has a 95% chance of operating failure-free. If you have 2 drives in a RAID0 array, the probability of the array NOT experiencing a drive failure in the next year is (.95 * .95), or 90.25%, which means that your odds of 100% data loss have jumped from 5% to 9.75%. Adding a third drive increases your failure odds to 14.26%, and so on.
........
[a href=\"index.php?act=findpost&pid=98566\"][{POST_SNAPBACK}][/a]
Jonathan, you say my formula is wrong and then use exactly the same formula and arrive at exactly the same result. At least we agree in math. As you can see above - 9.75% is exactly the number I arrived at and it is roughly double that of 5%, not square of 5%, which is what I was trying to prove since you stated:
Raid 0 2-drive arrays do not double the the risk of failure, they square it.
With respect,
--Misha
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Jonathan, you say my formula is wrong and then use exactly the same formula and arrive at exactly the same result. At least we agree in math. [a href=\"index.php?act=findpost&pid=98570\"][{POST_SNAPBACK}][/a]
Not to start an argument, but I think perhaps you're both wrong if you look at combinational probabilities...
So, I think the better formula would be: (n!/((k!)(n-k)!) * (p^k)((1-P)^(n-k)) where n = number of drives (2), k = number that would need to fail to cause an event (1), p = probability of failure of any drive (using .05).
Sooo... 2!/(1!)(1!) * .05^1 * (.95)^(2-1) = 2/1 * .05 * .95 = 2 * .05 = .095, or a 9.5% probability of failure in one year. (Okay, not appreciably different than your results, but I think more technically correct )
Ray, you're a statistics prof, right? Maybe you can shed some light on this for us...
Cheers,
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This is not unique to HDDs, or to any backup media. Quite the contrary, actually.
However, when people use HDD "backups", they seem to stick to the second half of their mirror as the backup. So, essentially, you have one backup medium for your data, not two. That is, original HDD and mirror HDD. Dual DVDs means that you have the original HDD plus two DVD copies. I admit that this wasn't clear from my post.
But there's another important difference between HDDs and optical media, is that the HDDs are more exposed to OS write errors, or problems from a faulty power supply, motherboard, controller, electrical black- or brown-outs, etc., since they're not WORM (write once, read many) media.
When I wrote that HDDs have a high probability of failing within a short time of eachother, that was not a joke. This has to do with the drives having very similar runtimes and working conditions. It is also likely that the drives were purchased at the same time, and therefore from the same production lot, which increases the risk of similar production anomalies.
With WORM media, it is common for you to, well, write once, verify the integrity, and then "forget it". This increases the likelyhood of detecting similar production anomalies in the media, compared to HDDs. What you cannot detect, of course, is how the media deteriorates with time; is the plastic acid free and does it seal well enough, is the dye pure and of a time-resistant type (e.g. advanced metal AZO) or not (cyanine or phthalocyanine), and so on.
I'd argue this issue is even more prevalent for DVDs/CD-ROMs, as people tend to burn a DVD, tug it in a pouch and forget it. If they need that backup years later they might see bitrot has taken its toll - this might be the case even with redundant DVD backups.
With HDDs you are generally copying data to the same HDD, thus ensuring its integrity every time you do so. How many people backing up on DVDs check their integrity periodically?
How many people backing up to HDD check their integrity periodically? I think the proportion of people verifying their backups are similar, regardless of media.
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I find the issue interesting because it highlights just how difficult it is to get to the truth of a matter like this; ie, reliability of optical media versus hard drive storage.
Generally, people are only motivated to speak out when they are angry or outraged and/or feel cheated or misled in some way.
If you were to conduct a poll on such an issue; example, how many of you have experienced CD/DVD failure, how many have not etc, those who felt aggrieved would be more likely to respond to the poll, so the result would be skewed in that respect, but perhaps even more significant, there would be no way of verifying whether or not the failed optical disc had, for example, been left baking in the sun in a parked car; whether it had been heavily scratched and/or subjected to extremes of environmental conditions, or, in the event of it being just tucked away in a sleeve, whether or not it had been properly recorded in the first instance.
Nobody likes to admit they are incompetent. It's very easy to forget that, say 5 years ago a particular disc was left on a car seat all day, baking in the sun, or that, despite a verification process being used at the time of burning, the disc was perhaps still not recorded properly and such verification was not confirmed after burning by opening a few images.
It's also too easy to confuse DVD drive/software incompatibilities with physical deterioration of the disc. I've had that problem myself too often. Occasionally, a DVD disc I've recently burned on my laptop cannot be read on one of my desktop computers, or perhaps just one folder on that disc causes Adobe Bridge to 'not respond', yet the same disc is perfectly readable on another computer. I don't pretend to understand why this should happen.
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Ray, you're a statistics prof, right? Maybe you can shed some light on this for us...
Cheers,
[a href=\"index.php?act=findpost&pid=98636\"][{POST_SNAPBACK}][/a]
Jack,
I'm not a professor of anything. Can I therefore claim to be relatively free of brainwashing, perhaps?
However, it seems to me it doesn't really matter which formula is more precise if the MTBF data you are using in the formulas are not precise, and as Jani has pointed out, even if the MTBF data supplied by the manufacturer was broadly correct, it wouldn't account for the changed odds due to the fact you might have 2 or more drives from the same batch, a slightly substandard batch which doesn't meet the manufacturers publish MTBF specs.
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Jack,
Perhaps the 3 examples of calculating the probability of a second hard drive failure could be considered as a type of formulaic pixel-peeping .
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Jonathan, you say my formula is wrong and then use exactly the same formula and arrive at exactly the same result. At least we agree in math. As you can see above - 9.75% is exactly the number I arrived at and it is roughly double that of 5%, not square of 5%, which is what I was trying to prove since you stated:
Raid 0 2-drive arrays do not double the the risk of failure, they square it.
With respect,
--Misha
Sorry, I'd just gotten off a 24-hour shift. You are squaring the (1-x) factor, at least for a 2-drive Raid 0 array. .95 * .95, etc. Jack, your question is valid for RAID5, since 2 drives have to fail simultaneously for the array to fail, but not for RAID0, where as soon as the first drive fails, you're screwed. Given the agreed meanings for x and n, and r as the repair/rebuild time factor, the correct formula would be:
(1-((1-x)^n)*(1-((1-x)^(n-1))*r
When one drive has failed, there is one less drive to create an additional failure. So the correct formula for a 4-drive RAID5 with a 24-hour repair/rebuild time is .1855*.1426*(1/365), or 0.274%. Jani raises some valid points about simultaneous failures, but calculating the risk factors for a power surge blowing several drives in the array simultaneously, or damage due to fire, flood, earthquake, terrorism, or human stupidity is a bit harder, as the risk factors are harder to quantify and may not even be known. So the 0.274% array failure risk is kind of a best-case-scenario based on competent setup, placement, maintenance, etc.
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However, it seems to me it doesn't really matter which formula is more precise if the MTBF data you are using in the formulas are not precise, and as Jani has pointed out, even if the MTBF data supplied by the manufacturer was broadly correct, it wouldn't account for the changed odds due to the fact you might have 2 or more drives from the same batch, a slightly substandard batch which doesn't meet the manufacturers publish MTBF specs.
In case anyone is confused about MTBF, I think it's worth pointing out that MTBF is not about individual drive reliability.
archive.org has a copy of IBM's explanation of how IBM calculated MTBF while they manufactured HDDs (http://web.archive.org/web/20001202154100/http://www.storage.ibm.com/storage/oem/tech/mtbf.htm)
It's a pretty good read.
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In case anyone is confused about MTBF, I think it's worth pointing out that MTBF is not about individual drive reliability.
[a href=\"index.php?act=findpost&pid=98678\"][{POST_SNAPBACK}][/a]
But surely in a sense it is. Perhaps I haven't understood the concept, so put me right if I haven't. The MTBF figures appear to be saying something like, 'If I use a 100 drives under the same conditions and to the same extent for, say half a million hours in total, then one of them can be expected to fail.
Another manufacturer might claim, 'If you use 100 of our drives under the same conditions, then they should last in total, one million hours before you would expect a drive to fail'.
The second scenario, with a quoted MTBF of 1 million hours would imply that the individual drives must be more reliable than in the first scenario where the MTBF is only half a million hours. Is this not the case?
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But surely in a sense it is. Perhaps I haven't understood the concept, so put me right if I haven't. The MTBF figures appear to be saying something like, 'If I use a 100 drives under the same conditions and to the same extent for, say half a million hours in total, then one of them can be expected to fail.
Another manufacturer might claim, 'If you use 100 of our drives under the same conditions, then they should last in total, one million hours before you would expect a drive to fail'.
The second scenario, with a quoted MTBF of 1 million hours would imply that the individual drives must be more reliable than in the first scenario where the MTBF is only half a million hours. Is this not the case?
The point is that MTBF can't be used directly for approximating the reliability of a single drive.
It's a number derived from the testing of a group from a batch of drives with that particular manufacturer.
It may be used for approximating the expected failure rate of a group of drives within their product life time.
As the IBM article said:
5. If I purchase 1000 drives with an MTBF of 1,000,000 hours, how many can I expect to fail over a five-year period?
[...]
In this example, because of statistical variation, there is approximately a 90 percent probability that the actual number of failures will be between 33 and 55.
If we use the same numbers for 100 drives, that gives us between 4 and 6 failures with approximately 90% probability. (Having 0.3 drives fail is the same as having 1 drive fail.)
In addition, it's worth mentioning that several drive manufacturers are on record stating that their "desktop" drives are not constructed for 24/7 use(!), but rather 8/7 or something like that. I believe IBM was one of those manufacturers (the DeskStar, AKA "Death Star" series).
This may skew MTBF numbers if the same drives are used 24/7, and the risk of failure is likely not simply tripled (but I'll refrain from speculating whether it will be worse or better than triple the risk).
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Jani,
I think my point was, if the MTBF figure can't be used directly to calculated the probability of failure of a single drive, then what other information can? If the MTBF figure is reliable and the situation and conditions it relates to are clearly specified, then the higher the MTBF figure is, for those same conditions, the more reliable each individual drive must be, on average. Is this not so?
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Jani,
I think my point was, if the MTBF figure can't be used directly to calculated the probability of failure of a single drive, then what other information can? If the MTBF figure is reliable and the situation and conditions it relates to are clearly specified, then the higher the MTBF figure is, for those same conditions, the more reliable each individual drive must be, on average. Is this not so?
There are other reliability indicators in the specification for HDDs:
- Product life-time/warranty
- Recommended usage (8 hours/day or 24 hours/day?)
- Average nonrecoverable read errors per bits read
- Average number of start/stop cycles before failure
And Seagate, for instance, is no longer using MTBF in their specification sheets, but rather "AFR" (annual failure rate). Their "high reliability" DB35 Series 7200.3 for use in DVRs boast 0.68% in this metric.