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Icy Dock ICYRaid MB662U3-2S Review

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scott_chegg 19th March 2013, 09:35 Quote
Good article. I'll get this in before anyone else does

"which is a fair price to pay for a portable and always up-to-date backup solution"

RAID is not backup.
Meanmotion 19th March 2013, 10:01 Quote
If you run in in RAID 1 it is.
BigM2006 19th March 2013, 10:07 Quote
Quote:
Originally Posted by Meanmotion
If you run in in RAID 1 it is.

No, in RAID 1 its redundancy.

RAID is not a backup solution, but can be used as the storage for backups.
Critically backups should contain versions of the data, so restorations can be completed.

With a RAID 1 array, if you delete the file it will be removed from both disks, meaning it can't be recovered if needed.
Gareth Halfacree 19th March 2013, 10:11 Quote
Quote:
Originally Posted by Meanmotion
If you run in in RAID 1 it is.
<sysadmin hat>No, it isn't. RAID1 is for availability, not backup. Quick thought exercise: you have your data stored on a RAID1 array. You accidentally delete a file. How do you get that back? Second thought exercise: you have your data stored on a RAID1 array. You suddenly realise that you've been overwriting the master copy of a file, rather than your working copy - and you need to go back to the version you had a month ago. How do you do that? Third thought exercise: you have your data stored on a RAID1 array. You realise that your entire document archive got infected with a virus six months ago. Nothing can clean the virus out. How do you get your six-month old versions back?

The answer, in each case, is "you can't." And that is why RAID is not a backup.</sysadmin hat>

No, but seriously: RAID can be part of a backup solution - I have a btrfs RAID1 array on two external drives connected to a Raspberry Pi as a cheap NAS alternative, and that's where I store backups of my desktop - but the backups don't rely on RAID, they're actual backups created with Duplicity. I can roll any file back to any day since I started the backup routine. Want to restore my scratchpad text file to the version from the 1st of January 2013? Not a problem. Suddenly realise I actually needed that folder I deleted three weeks ago? Here it is, good as new.

That's a backup.
scott_chegg 19th March 2013, 10:37 Quote
Exactly Gareth. RAID provides hardware redunancy against a disk failure. If you trash the data on a RAID array you simply have two copies of trashed data.

On my Ubuntu NAS I have 2 data disks. Primary disk and secondary disk. My shares are on the primary disk. Every hour RSYNC copies changed data to the secondary disk but doesn't delete any files of the secondary disk that aren't still present on the primary disk. Once a week another RSYNC script runs that syncs the 2 disks completely so If my data on the primary disk is deleted I can recover it from the secondary disk for a week. I also have a USB disk attached that is sync'ed daily and a USB disk in my desk drawer at work that I take home and sync weekly then return to work. That is a backup solution. Not as thorough as the solution Gareth has just described but still a backup solution that protects me far more than RAID.
Meanmotion 19th March 2013, 11:40 Quote
There is such a thing as context, people:

"RAID 1, on the other hand, is likely to hold much greater appeal in the ongoing fight against drive failures. Thankfully, performance in this mode is rock solid, as it rarely falls behind standard single drive set-ups by more than a few percent, which is a fair price to pay for a portable and always up-to-date backup solution."
BigM2006 19th March 2013, 12:05 Quote
Meanmotion, your original comment was aimed at Scott's comment "RAID is not backup".
In whatever context you choose, that statement is correct.

RAID 1 offers additional redundancy to a component that has an increased failure rate. It does not provide a backup functionality. It simply offers a redundant copy of the current data.

Also worth noting that a RAID controller failure can kill a RAID1 array, again re-enforcing the need for a proper backup solution.
Meanmotion 19th March 2013, 12:38 Quote
The original comment was quoting the article therefore any response should be in the context of the article.

I'll concede that, despite the preceding sentence, the use of backup could be misleading so will change it to redundancy.
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