Mais Alain, don't those drives consist of two 750GB drives chained together in one case, thereby doubling your chances of catastrophic drive failure for each one?
Nill
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www.toulme.net
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Mais Alain, don't those drives consist of two 750GB drives chained together in one case, thereby doubling your chances of catastrophic drive failure for each one?
Nill
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www.toulme.net
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I agree it is a risk, but I need large storage space. Right now I have about 4 TB online. Everything is backed up twice, so even if a drive crashes nothing is lost.I don't understand the point of these doubled drives though. In what way are they better than two separate 750GB external drives? It seems to me all they accomplish is doubling your chances of losing twice as much data. (Does that equate to 4x the risk?)
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...By the way, this looks like a nice product. I've been pushing Samy's to start carrying a CalDigit item:Something like that holding four drives instead of two, configurable as RAID5, and with a handle on top for portability, would seem just about ideal to me. SATA might be preferable to firewire though.
http://www.caldigit.com/FireWireVR.asp (http://www.caldigit.com/FireWireVR.asp)
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Has it not been established that those who are the least bit paranoid about data loss, should back up their images on optical media like DVDs.
I know it's a bit tedious burning DVDs that hold only 4.4Gb, but we now have Blu-ray discs that hold 25Gb.
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Has it not been established that those who are the least bit paranoid about data loss, should back up their images on optical media like DVDs.
I know it's a bit tedious burning DVDs that hold only 4.4Gb, but we now have Blu-ray discs that hold 25Gb.
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I have everything backed up on DVD's as well.
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Besides, you'll have to check the DVDs or re-burn them every year or so to ensure they're not rotting. [a href=\"index.php?act=findpost&pid=93563\"][{POST_SNAPBACK}][/a]
Nonsense! Have you ever thought of engaging in a bit of introspection to check your level of paranoia .
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I don't understand the point of these doubled drives though. In what way are they better than two separate 750GB external drives? It seems to me all they accomplish is doubling your chances of losing twice as much data. (Does that equate to 4x the risk?)
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Something like that holding four drives instead of two, configurable as RAID5, and with a handle on top for portability, would seem just about ideal to me. SATA might be preferable to firewire though.
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Paranoia? It's a studied fact that DVDs rot. I have literally hundreds of DVD-Rs from less than 5 years back that are unreadable.[a href=\"index.php?act=findpost&pid=93578\"][{POST_SNAPBACK}][/a]
Wow! I can't understand that at all. All my ultra budget CDs recorded more than 10 years ago are still perfectly readable. I have no instances of DVDs that are unreadable, recorded 5 years ago (or so, or more).
Have you been the victim of fraud? Perhaps some company selling a batch of reject DVDs that they managed to acquire for nothing?
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Umm..... 4 terabytes on DVDs? That's.... *calculates* .. *shocked* .. *doublechecks* ... almost one thousand (1,000) DVDs...
You, sir, either have the patience of a saint or a very patient assistant.
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For most people, doing a single backup is difficult enough. So to be able to write it to one device that automatically makes two copies makes sense. There are really no advantages to archiving to RAID 5 over RAID 1 in this type of scenario. In RAID 1 everything is written twice. It's only when people use RAID 0 (striping) that the failure rate increases.Now that does make a bit of sense, although (a) I suspect that most of these drives are being used as 1.5TB RAID 0 (or JBOD or something worse?) drives, not as 750GB RAID 1, and (b) there are still advantages to simply having two redundant external drives over RAID 1, e.g., operator error, etc.
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Hmmmm... Like this?Yes exactly! Those are a little pricy though. Mac Gurus has some enclosures that I've been looking at...
http://www.wiebetech.com/products/rt5.php (http://www.wiebetech.com/products/rt5.php)
I like these too:
http://www.kanotechnologies.com/products/SV3X500R5S.cfm (http://www.kanotechnologies.com/products/SV3X500R5S.cfm)
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Now that does make a bit of sense, although (a) I suspect that most of these drives are being used as 1.5TB RAID 0 (or JBOD or something worse?) drives, not as 750GB RAID 1, and ( there are still advantages to simply having two redundant external drives over RAID 1, e.g., operator error, etc.
Clearly there's no benefit of RAID 5 over RAID 1 in a two-disk array, but my whole point is that I don't *see* the point of two-disk arrays. RAID 5's reliability benefits kick in at 3+ disks.
Nill
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www.toulme.net (http://www.toulme.net)
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Now that does make a bit of sense, although (a) I suspect that most of these drives are being used as 1.5TB RAID 0 (or JBOD or something worse?) drives, not as 750GB RAID 1, and ( there are still advantages to simply having two redundant external drives over RAID 1, e.g., operator error, etc.
Clearly there's no benefit of RAID 5 over RAID 1 in a two-disk array, but my whole point is that I don't *see* the point of two-disk arrays. RAID 5's reliability benefits kick in at 3+ disks.
Nill
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www.toulme.net (http://www.toulme.net)
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I don't see the advantages of 2 drives vs RAID 1. Do you mean being able to take one off site?There's that, plus if you accidentally permanently delete or otherwise hose a file or folder on a RAID 1 setup, by definition you do it on both disks, right? With two separate disks — i.e., two separate backups — you reduce that risk significantly it seems to me.
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I could be wrong, but my understanding is that with RAID 5 you lose all your data if your controller card malfunctions (short circuit, lightning damage, etc.). With RAID 1 you don't have that problem.If a controller malfunctions there's no telling what could happen, no matter what RAID level - you may get lucky or not. If it just stops functioning, no harm, just replace it. But if it goes medieval on your drives, well that's that. But the same would apply to a normal disk controller, so there's no saving grace here, RAID or not. I mean, lightning bolts don't discriminate against RAID disks particularly - any drive can be fried equally . However, a fault-tolerant RAID array could minimize your probability of failure, because if only one drive is fried you can recover.
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CDs and DVDs aren't really comparable as DVDs have much higher data density and as thus are more susceptible to rotting.i've had quite a few dvd-r discs rot over time. sometimes as soon as a few months. rough guess is that ~10% will fail within 1-3 years. it's harder to get catastrophic failure with hundreds of independent image files on a dvd-r, but a patch of rot will stop a movie cold. i see that all the time.
It's possible that I'm a victim of fraud. But there are plenty of studies which suggest that "normal" recordable DVDs have a _practically_ limited shelf life. Limited in the sense that I nor any professional should trust them to work indefinitely. If you just burn two sets once, put them in a climate-controlled archiving cabinet and leave them for ten years, I wouldn't be surprised if there are quite a few ones that aren't readable.
Thankfully (?) tech advances at such a pace that people are re-burning or re-archiving files to different media every few years.
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i've had quite a few dvd-r discs rot over time. sometimes as soon as a few months. rough guess is that ~10% will fail within 1-3 years. it's harder to get catastrophic failure with hundreds of independent image files on a dvd-r, but a patch of rot will stop a movie cold. i see that all the time.
ted
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You're just lucky, Ray.
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You're just lucky, Ray.i have to concur. at first i thought it was a disc quality issue so i only used name brand, store bought discs. Verbatim, Maxell, Apple. Not that they make their own, or do much beyond repackaging. I'm sure there's a list of who makes what somewhere on the internet. Following discussions of disc rot on the internet led me to a couple of supposedly high quality, japanese original manufacturer 'gold label' discs. much higher cost, but would be worth it if they didn't fail. or let me stop worrying about failure in my backups.
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Hmm! How odd! I was importing DVD movies from the US from the time the first DVD-ROM player became available in Australia; before there were hardly any titles available in Australia. I had my Creative Labs DVD player permanently set to Region 1, before I discovered a 'crack'.
I haven't come across a single disc, from those early years, that fails to play, whether from disc rot or any other cause. But I have bought the occasional pirated movie (from Malaysia and Thailand) that failed to play despite being new, and I have recorded images on a DVD disc which failed to play immediately after recording.
I have no reason to suppose that 'genuine' discs that have met standard QC requirements and that have been recorded properly should give any trouble. That's just my experience.
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So, once again, DVDs are way too finicky for me to trust for backups. This holds even now when the tech is mature, as there is a much better alternative in external HDDs and RAID arrays.So far, the "external HDDs and RAID arrays" crowd have been very good at dissing DVDs.
Now I have a batch of DVDs which can only be read with that burner as others won't work with them. That's only with one brand.
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An alternative to disk drive "backups" is to make tape backups, but then you need to avoid the bad kinds of backup tapes (DAT, for one) and try to find the ones that have a fairly long storage life (S-DLT, maybe, or LTO-3). But of course, even the cheap ones aren't really cheap in terms of absolute number of dollars (http://www.exabyte.com/products/products/get_products.cfm?prod_id=601).
And you're still not safe from the issue of at least checking your data integrity, or migrating your data.
Got a headache yet? Good, because I certainly do.
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I stand by my choice of HDD backups. As you said, there is a need to re-migrate to new media every few years whether one goes for CD, DVD or HDD. But as I've pointed out earlier, migrating hundreds - or even tens - of DVDs is an order of a magnitude more pain in the ass than migrating a few HDDs.
While tape is a decent solution, they are way too expensive as you point out, and due to them lacking random access are limited in their use.
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The first few hard drives I ever owned (the first being an 850mb Western Digital) have all failed, after 10 or 12 years and sometimes well before that. Not a single optical disc has yet failed in that period. When it does, I'll let you know. (Are you going to be around, on this site, in another 10 or 20 years? Maybe I'll catch up with you on another site ).
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If you want the most secure solution, build a dedicated raid 5 array, and rebuild it with new discs every 5 years. As they fail individually in between main builds, you lose nothing.
You can build a 1TB array with external cabinet for less than $750 right now, and that will only be cheaper in the future.
Big deal.
I run a 1TB raid 5 array in my system right now, and it cost me $600 in drives.
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You're telling me you've used 10-year-old HDDs? That's, what, 300MB and slow as molasses?
Anyway, it appears to be a moot argument. It's your time and money you're throwing away.
If your RAID card fries, so does your data (most likely and unless you want to spend thousands on data recovery service which might or might not recover anything).That depends on how the controller "fries". If it destroys the information stored on the disks, too, then you're out of luck.
So you still need backups even if you're running a redundant RAID setup.As I've mentioned in another thread, RAID 5 isn't the "most secure" solution as kaelaria touts.
But damn, prices really have come down. I'm definitely getting a RAID 5 finally when I get a new computer.
As a result, the Chernobyl accident caused a great deal of consternation amongst people living in the vicinity of the accident. Women had abortions, as it now seems, for no good reason at all. As some great American president (or important historical figure) said (who was that?), the only thing we have to fear is fear itself.I am one of those people who have received moderate amounts of radiation because of that accident.
Whilst it's true that some people died who were very close to the accident and who received massive doses of radiation (and I hope that I am not seen as trivialising their families' grief), there are lots of people who received moderate amounts of radiation, who've been quaking in their boots for the past 20 years, and who are still as fit as a fiddle.
An analysis of the wildlife in the close vicinity of the accident revealed very surprising results. The researchers expected to find all sorts of mutant rats and mice with two heads and three ears, or perhaps no wildlife at all. On the contrary, wildlife was thriving without a hiccup. Moderately strong radiation levels just seemed to have bounced off their back. In fact, it now seems that relatively small amounts of radiation, up to 100 millisieverts (per year) are actually beneficial to us. They stimulate our immune response. An analysis of areas in the United States that have strong, natural background radiation, have shown that people who live in such areas have less cancer, statistically, than people who live in areas with low background radiation.The "strong, natural background radiation" is peanuts compared to the radiation in areas that were close the Chernobyl accident.
However, in your situation I see the problem. To transfer 1TB of images to DVD would be a mammoth task. Pity you haven't been doing it regularly by degrees. You could then have peace of mind .
On the cost issue, I should mention that a LaCie 300GB external hard drive, in Australia, costs about A$1 per gigabyte, maybe a bit less now. Blank DVDs are about 10-20 cents per gigabyte.
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I just checked prices here in Europe. 3.5" hard drives cost ~€0.20 per gigabyte (with €20-50 for the external casing, bringing an external 500GB drive to 25 eurocents per gig) while DVDs cost €0.10 in 100 DVD spindles - their price has gone down drastically here in the past 6 months. So you were right, DVDs are cheaper. But if one puts any money on time spent backing up and verifying it's a no-brainer.Since you're using harddrives, you'll be replacing them every three years or so anyway.
BTW, I doubt hard drives cost three times as much in Australia than in already expensive Europe as your numbers suggest. Perhaps you're looking at the 2.5" prices or prices of some ultra-fast server drives?
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200 DVDs €174 + 200 DVDs €120 + 200 DVDs €90 + 200 DVDs €70.
DVD cost, presuming that you change no other components: €442.
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Strange things happen (what you least exRAID 0 isn't really RAID.
I Currently: Have a Raid system (raid 0) then backup on an external Maxtor
that stays on site another backup on Maxtor goes home (along with archival DVD Gold backups at home).
Those prices seem a bit inflated, Jani. Right at the moment I could buy 200 DVDs for just 46 Euros at a local store. Are you referring to the gold plated variety?No, definitely not gold plated.
WOW I can't believe the level of absolute PARANOIA around here...lol!! Either that or some of you should have auditioned for Monk
...
You guys sure are entertaining when you try and give computer advice
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I'm looking at prices at http://www.computeralliance.com.au/parts.aspx?qrySubCat=HBK (http://www.computeralliance.com.au/parts.aspx?qrySubCat=HBK) which is a local computer store in Brisbane with some of the best prices in town. Internal hard drives vary from around 40 cents to 70 cents per GB, but external hard drives are more expensive, ranging from a bit under a dollar per GB to a bit more than a dollar. A$1 is 0.60 Euros. There are always a few run-out models that are on special and might bring those prices down a bit.
Currently in that store, the best value DVDs are by LG, 16x in spindles of 50 for A$19. That's just 8.4 cents per GB.
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I am one of those people who have received moderate amounts of radiation because of that accident.
I have, however, not been "quaking in my boots", but others certainly have.
I feel comfortable that the doses of radiation haven't been critically high, and that the chances of me developing cancer aren't significantly higher because of that accident.
The "strong, natural background radiation" is peanuts compared to the radiation in areas that were close the Chernobyl accident.
Areas closest to Chernobyl, such as the town of Zaborye in Brjansk, Russia, had concentrations of cesium-137 of above 100 curies per square km.
In an area of approximately 10 300 square km areas around Chernobyl, the concentration of cesium-137 is greater than 15 curies per square km, or more than half a million becquerel per square meter.
An additional 28 600 square km in Russia, Ukraine and Belarus measured 5 curies or more per square km.
Certain areas of Norway received concentrations of about 100 000 becquerel per square meter, enough to make lots of reindeer, sheep and mushrooms unfit for human consumption. (Peruse a map if you don't know how far away that is ...)
The half-life of cesium-137 is about 30 years.
Gomel in Belarus, 130 km northwest of Chernobyl, still has a concentration of 1-5 curies per square km.
A total of eight to ten million people still live under conditions that are more radioactive, but it's suspected that tens of millions risk serious health consequences because of radioactive materials transported by water. How great these risks are is debated, however.
(Feel free (http://www10.antenna.nl/wise/index.html?http://www10.antenna.nl/wise/449-450/4.html) to read (http://www.stuk.fi/sateilytietoa/sateily_ymparistossa/itameri/en_GB/laskeuma/) a bit more (http://en.wikipedia.org/wiki/Chernobyl_accident))
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Practically the whole territory was heavily contaminated by radionuclides. More than 1.8 million people are still living in heavy polluted territories. The radiation dose they receive on average amounts to 15 mSv (milliSievert) a year.
Nearly 20 years after the disaster, according to the Chernobyl Forum, no evidence of increases in the solid cancers and, possibly more significantly, none of the widely expected increases in leukemia have been found in the population.
The problem for hard drives is remote location storage of backups, where DVDs win for convenience of transport. If you have access to networked storage, hard drives win on convenience, too.
And arguably, it's easier to verify the data integrity with hard drives.
But given the very small additional cost -- both in time and money -- of creating DVD backups as you go, it is prudent to do both: redundant hard drives and redundant DVDs.
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You can buy the external HDD as a package and pay premium, or you can buy a "normal" 3.5" HDD and an external casing on the cheap. My prices are based on the latter as I pointed out in my earlier post, and are significantly cheaper than buying an expensive external HDD package.
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According to the first article you referred to, in Belarus there are 1.8 million people still living in heavily polluted areas and receiving 15 milliSieverts of radiation a year. Is that a typo? It is now thought that doses up to 100 milliSieverts can be beneficial.When you write "it is now thought that ..." you imply that this is the general consensus.
I backed up to DVD for about six months then lost interest. There just got to be too many of the darn things. And as much of a PITA as backing up to DVD is, I don't even want to think about having to restore half a TB or more from DVD. Yikes!Yes, that is a bummer, isn't it?
And I still don't understand the appeal of a mirroring RAID system (e.g., RAID10) over, say, RAID5 plus redundant on- and off-site HDD backups. Yes it provides more protection against some failure in the RAID itself, but not against all the other stuff that can bite you... OS burps, viruses, surges, operator headspace errors, etc. Anything that writes a bad file to, or deletes a good file from, one side of the mirror does the same to the other side, does it not? What good is that? I'm sure I'm missing something here.That is correct, but what good is RAID 5 or any kind of redundancy in the same system?
My live data is on a 1.1TB RAID5. It backs up, automatically and nightly, to external firewire drives. Those get backed up, manually and weekly or so, to another external drive that otherwise stays at my next door neighbor's.As long as you verify that the data is the same in both backups (use e.g. MD5 checksums of each file, stored to a list, and an MD5 checksum of that file, too), there is nothing inherently wrong with that.
Hmmm... I probably shouldn't be backing up from my backups, should I. Maybe I'll change that.
If your RAID card fries, so does your data (most likely and unless you want to spend thousands on data recovery service which might or might not recover anything). So you still need backups even if you're running a redundant RAID setupno it doesn't.
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You might also want to consider a UPS to protect against brown-outs and brief black-outs.
As long as you verify that the data is the same in both backups (use e.g. MD5 checksums of each file, stored to a list, and an MD5 checksum of that file, too), there is nothing inherently wrong with that.
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That is correct, but what good is RAID 5 or any kind of redundancy in the same system?Reliability. In the nine months I've been running that RAID I've had a drive fail twice. Now maybe that's just exceptionally bad luck, but it happened. But when it happened, I lost absolutely nothing other than the small amount of time it took to yank out one drive and plug in another. Then the RAID rebuilt itself. No downtime, no restore, no "Yikes, is my backup good?" — just roll on.
However, OS "burps" that destroy already stored data are extremely rare, even with Windows, at least as long as you use NTFS as your file system instead of FAT. Malware that destroys data is perhaps a bit more frequent.I have those things, of course. User stupidity is my greatest exposure, and as I am the user, that exposure is exceptionally high in my case. So I need systems that protect against that exposure as well as all the others. ;-)
...Surges? You don't have a surge protector? That's irresponsible, and it's such a cheap measure, too.
You might also want to consider a UPS to protect against brown-outs and brief black-outs.
As long as you verify that the data is the same in both backups (use e.g. MD5 checksums of each file, stored to a list, and an MD5 checksum of that file, too), there is nothing inherently wrong with that.That makes sense. I am using checksums on my compares, but not against a stored list. I'll have to figure out how to do that.
What's the checksum of a checksum for? I don't know much about the MD5 algorithm itself, but doesn't it include data in itself to verify its own integrity? This would yield a checksum of a checksum useless.No, it's not a checksum of a checksum.
Reliability. In the nine months I've been running that RAID I've had a drive fail twice. Now maybe that's just exceptionally bad luck, but it happened. But when it happened, I lost absolutely nothing other than the small amount of time it took to yank out one drive and plug in another. Then the RAID rebuilt itself. No downtime, no restore, no "Yikes, is my backup good?" — just roll on.In that case I misunderstood you, I thought you objected to this, because this is the point of a stripe of mirrors (RAID 10), too, only that you'll have better write and read performance, as well as better protection against failures (up to fully half the number of disks may fail without data loss).
In that case I misunderstood you, I thought you objected to this, because this is the point of a stripe of mirrors (RAID 10), too, only that you'll have better write and read performance, as well as better protection against failures (up to fully half the number of disks may fail without data loss).Well I suppose I'm thinking also from the standpoint of cost/benefit at the very bottom end of the scale (where I dwell). Of course if cost is no object then RAID10 or even RAID6 affords additional reliability. It just seems to me that RAID5, at the cost of only one additional drive's capacity, provides a very significant reliability enhancement. Beyond that, I'd personally rather spend my few available dollars on redundant backups that protect me better against my biggest threat — my own screw-ups. ;-)
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No, it's not a checksum of a checksum.
It's a checksum of the file containing all the other checksums.
That way, you can check -- with a reasonable degree of reliability -- whether your list of checksums is correct or corrupt.
Of course, that doesn't help you much if you find that the list is corrupt, but if you have another copy of the list, ... Storage is cheap for this kind of things, so having multiple copies of the checksum list is easy and prudent practice.
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Since you were so fond of quoting only a small part of a pretty long Wikipedia article, only to support your personal view, here's another bit of a Wikipedia article for you:
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RAID 0 isn't really RAID.
RAID = Redundant Array of Inexpensive Disks
There is no redundancy in RAID 0.
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Well, that's splitting hairs.Eh, no, it isn't.
But I'm still under the impression that an MD5 checksum already includes integrity verification in itself. ie. if the MD5 checksum file is corrupted, it won't work nor give false results with the actual backed up data. Therefore getting checksums of checksums isn't necessary or even useful - just having multiple copies is enough. Correct me if I'm wrong.You're wrong; the checksum isn't self-correcting.
Exactly, this is why I also beckup to external maxtors and the DVD'sNo, that's exactly what you haven't got.
Raid 0 (as best I can surmise) is mostly good when one hard drive crashes. You then have all the data on another mirror drive.
What I'm suggesting here is, if it were possible to collect the facts on all the DVD discs that have ever been produced, remove all the scams from the equation where known rejects have been sold, and remove all the instances where people have unwitingly applied adhesive labels to their discs which have chemically attacked the disc etc, we might find that only, say 0.000001% of those billions of discs have suffered from physical deterioration that makes them now unreadable, ie. one in a million.While it's unlikely that the figures would be this good -- one in ten thousand or one in a thousand seems more likely -- I agree with the principle.
I have a stack of failed recordings about 9" high. I've kept the discs because I thought I might find a decorative use for them .You could, I suppose, run them carefully (hehe) through your microwave, the patterns will be different for each disk, and they might actually be cool to look at.
Nice image — glad it still loads. ;-)
Nill
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www.toulme.net (http://www.toulme.net)
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Eh, no, it isn't.
There's a pretty big difference between doing a checksum of each checksum, and doing a checksum of a huge list of checksums.
You're wrong; the checksum isn't self-correcting.
...Is it worth scanning them to preserve the memory for future generations that might not give a stuff? Should I scan them purely for the experience of nostalgia I might get and the satisfaction of doing the best job I can in extracting the most detail? Have I got better things to do?Yes; yes; possibly, right at the moment, but at some point...
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Here's image no. 14 on the same disc. ...Another excellent image, and the scan might respond to some sharpening.
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Yes; yes; possibly, right at the moment, but at some point...
Nill
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www.toulme.net (http://www.toulme.net)
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Dang, if your eye was that good 42 years ago, I don't even want to see any of your current work.
Nill
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www.toulme.net (http://www.toulme.net)
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And I still don't understand the appeal of a mirroring RAID system (e.g., RAID10) over, say, RAID5 plus redundant on- and off-site HDD backups. Yes it provides more protection against some failure in the RAID itself, but not against all the other stuff that can bite you... OS burps, viruses, surges, operator headspace errors, etc.[a href=\"index.php?act=findpost&pid=95485\"][{POST_SNAPBACK}][/a]The main advantages of RAID 10 are the better redundancy (under certain circumstances), faster write times, and the fact that you could recover the whole array from a single disk from each mirror pair. I use it in my data array but my backup array which has the last 3-5 images of each of my logical system & data disks is RAID 5. My system disk is striped (RAID 0, which as Jani mentions has no redundancy).
Has tape really gotten price competitive with HD's?Yes and no.
If you want to build a 12-disk RAID 5 with 750 GB drives, that will cost quite a bit of money. If you want to purchase a ready-made solution, it will cost a bit more.I put a 12 disk raid 6 array for $3500 into my desktop computer.
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