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Author Topic: Best way to clone two RAID 0 external storage units?  (Read 8875 times)

tsinsf

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Best way to clone two RAID 0 external storage units?
« on: April 07, 2014, 05:00:43 pm »

After great responses to an earlier question, I have another. I'm exploring options for external storage when I upgrade to Mac Pro or the new Mac Mini (if it ever happens). What would work perfectly for me is to buy two external thunderbolt drive enclosures configured to RAID 0 (either 8TB or 12 TB using two or three hard drives) and use one for storage and the other as a cloned backup. Will Super Duper do this without a lot of hassle and fine tuning? If not Super Duper, any other better cloning software? Thanks!!
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BrianWJH

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Re: Best way to clone two RAID 0 external storage units?
« Reply #1 on: April 07, 2014, 06:01:25 pm »

The terms 'backup' and raid0 are mutually exclusive.

Brian.
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tsinsf

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Re: Best way to clone two RAID 0 external storage units?
« Reply #2 on: April 07, 2014, 06:23:10 pm »

I emailed SuperDuper and they claim their software will clone a Raid 0. I'd like to know if anyone has experience actually doing this. I'm looking for advice, not unhelpful pronouncements.
« Last Edit: April 07, 2014, 06:27:49 pm by tsinsf »
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Farmer

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Re: Best way to clone two RAID 0 external storage units?
« Reply #3 on: April 07, 2014, 08:53:16 pm »

I would be very reluctant to rely on cloning of a RAID device.  Copying or Backing up, sure.  But actualy cloning (sector level copying, basically) complicates things a lot.  Regardless of what someone might say their product can do, I think it's a bad idea.

I would simply run a backup of one to the other, which may be what the vendor means by "cloning" rather than the Ghost style sector level cloning most people associate with the term.

The point made by Brian is not unhelpful.  Many people assume that items that are RAIDed are backed up and secure.  I realise you're talking about a second array to act as a backup, and that's a good thing, but you need to mindful of the capacity to restore from that in the event that you lose access to your RAID controller or the device itself becomes faulty (you can't always just grab one array and put it in another device and make it work).

Typically, you want your backup to be as vanilla and accessible as possible if it's a true backup.  That would mean a series of individual 4TB drives to copy the contents of your working RAID array.  And then moving them offsite or copying them to an offsite set as well, if you really want protection.
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Phil Brown

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Re: Best way to clone two RAID 0 external storage units?
« Reply #4 on: April 08, 2014, 07:29:56 pm »

I don't think the OP is talking about RAID being a backup, which as everyone correctly points out, it isn't.
He is talking about buying two boxes from what I can see.

For those that are still not sure, RAID provides absolutely no backup, zero, zip, none. If you disagree then great, as there is to much competition out there.

I have a similar two x 2GB drive giving 4GB backed up using Time Machine to a rotating 3 external drives.
The problem is that if one or both of the storage drives fails then you have to rebuild the device from scratch and that can take a long time. If you did use raid for storage also then you would not lose productive time.
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Schewe

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Re: Best way to clone two RAID 0 external storage units?
« Reply #5 on: April 09, 2014, 01:55:25 am »

I emailed SuperDuper and they claim their software will clone a Raid 0. I'd like to know if anyone has experience actually doing this. I'm looking for advice, not unhelpful pronouncements.

Well, I use Carbon Copy Cloner not Super Duper but for the last few years, I've used CCC to backup my Raid 1 (RAID 0), to Raid 2 (also RAID 0) and then a final external RAID 5 drive each and every nite (at about 4AM). Cloning one drive to another drive whether or not it's RAID o, 1, 5, 6 or whatever, should provide you with an exact copy (including the creation/modification dates) from one drive to another. I would argue that a "clone" is perhaps better than doing a "Finder Copy" because a finder copy doesn't maintain the modification date/time while a clone will (at least that's my experience).

YMMV and I don't offer a money back guarantee!
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Farmer

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Re: Best way to clone two RAID 0 external storage units?
« Reply #6 on: April 09, 2014, 05:22:29 pm »

I guess it depends on what you mean by cloning.  To me, it's a sector level copy - it doesn't read files, it reads sectors and replicates them (thus you replicate the file system from one device to another, not just the files - true cloning/ghosting/etc can write to an unformatted device and will include MBRs and other related data).

The level of copying/cloning to which Schewe refers is available through good software (such as he's obviously using), as opposed to just a copy command (although even that can be told to retain attributes quite easily).  I agree it's important to maintain those attributes when backing up.

Again, backing up from one RAID array to another is not an issue and done regularly.  Cloning, though, in the true sense, could present problems and I don't see the benefit.  Also, I maintain that at least one copy of your data being used as backup should not be on a RAID array to prevent reliance on particular hardware or software implementations of the RAID.

I think the advice from everyone is applicable regardless of terminology.
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Phil Brown

tsinsf

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Re: Best way to clone two RAID 0 external storage units?
« Reply #7 on: April 09, 2014, 06:12:11 pm »

Thanks for all the comments!! Could you educate me a little bit more? I'm still fuzzy on the difedence between
copying and cloning. I've been using SuperDuper for years, every night. It just adds the new data since my last backup. Is it copying or cloning? What is a sector level copy? What is the difference between replicating the file system and not just the files?  Thanks again!!
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Schewe

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Re: Best way to clone two RAID 0 external storage units?
« Reply #8 on: April 09, 2014, 06:30:45 pm »

I guess it depends on what you mean by cloning.  To me, it's a sector level copy - it doesn't read files, it reads sectors and replicates them (thus you replicate the file system from one device to another, not just the files - true cloning/ghosting/etc can write to an unformatted device and will include MBRs and other related data).

Yep...there are levels of "cloning"....a bit for bit clone isn't something that can be done really easily. I have done a real clone using Retrospect where the end result was a bit for bit clone of the original drive (including any drive problems the original drive might have).

A more generic cloning such as what CCC or SuperDuper do is not a true clone but it is more advanced than a simple finder copy. I get the impression (but don't know for sure) that CCC uses a combination of terminal control and Applescripts to accomplish it's cloning.
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Farmer

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Re: Best way to clone two RAID 0 external storage units?
« Reply #9 on: April 09, 2014, 08:59:31 pm »

Thanks for all the comments!! Could you educate me a little bit more? I'm still fuzzy on the difedence between
copying and cloning. I've been using SuperDuper for years, every night. It just adds the new data since my last backup. Is it copying or cloning? What is a sector level copy? What is the difference between replicating the file system and not just the files?  Thanks again!!

For practical purposes in relation to doing your backups, the answer is "it doesn't matter" :-)

But for you general interest, it basically boils down to this:

1. Cloning (real cloning) means making an identical replica.  So if Drive A is cloned to Drive B, so far as any computer looking at it would think, they are the same drive in every respect.  The formatting of the file system, the attributes of files, any errors etc, are all transferred over as it's not looking at whole files, but rather the sectors on the hard drive and copying them over.  This is where programs like Ghost live in the scheme of things and it's used when you want to exactly replicate a drive (for example, rolling out a particular build to multiple computers, to avoid having to go through the installation process on each one).

2. Copying is copying.  As Schewe noted, there are different levels.  Some just copy a file and the new copy has a new timestamp and different attributes etc.  Some do an identical copy, which means the copied file looks exactly like the original one, but could be anywhere - not necessarily cloned onto an identical device.  This is what good backup software does (as well as making copies of all the hidden files and so on).  You can also do it manually if you know the settings.

What your SuperDuper is doing is normal, incremental back up.  This means it has an original version (the first time it backs up) and then it just has new/changed/deleted files in the incremental backups, meaning it's pretty quick and easy.  From time to time, most people do a "full" backup, to give a new starting point and so that the incremental changes don't go on forever (incremental backups do have some minor risks if left for a long time but I haven't really heard of serious problems in a long time).

Essentially, backing up using SuperDuper or CCC or any of the other software mentioned from one array to another should work very well.  Don't worry about "cloning".  Do consider having a non-RAID backup of your stuff, though, so you're not reliant upon specific hardware or software to recover your data.

Hope that's been of some assistance!
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Phil Brown

tsinsf

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Re: Best way to clone two RAID 0 external storage units?
« Reply #10 on: April 09, 2014, 11:16:54 pm »

Now I get it. Thanks!
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Lightsmith

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Re: Best way to clone two RAID 0 external storage units?
« Reply #11 on: April 16, 2014, 07:22:08 pm »

I would never put important data on a RAID0 box. DASD is so cheap that there is simply no reason not to go to RAID1 for this purpose. With RAID0 you double your chances for losing data with a hardware failure and with hardware there is always going to be a failure.
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