Has RAID ever saved you?

[RudePuppy]

First, it looks like this should be called the RAID forum, not General Hardware. Looks like every one is obsessed with RAID.

There are plenty of posts about RAID and performance, the wonders and futility of it all, but I am just tired of backing up all my important bits. So here's the question: for those of you running with a redundant RAID level, whether it be 1, 5, 10, 110, 220, etc., has it ever saved your data?

What I am really curious about is how you recover from a drive failure with RAID. Is your machine still perfectly operational but no longer redundant, or do things come to a grinding halt until the failed drive is replaced? Cant you still boot? Do you have to replace the failed unit with an identical drive? How long did it take to rebuild the array? Was the machine functional during the rebuild?

There are probably a dozen more questions I could ask, so I'll sum it up this way: If you have successfully recovered from a drive failure thanks to RAID, please share your experience in detail. Your contributions will be appreciated by all.

 

[ShadowBlade]

welcome to AT
that all usually depends on the controller (i think)

 

[Concillian]

Yes it is dependent on the controller. I run RAID 5 with 4 drives and have never had an issue (knocks on wood). However, before I put anything good on the drives I did load up an OS, moved some meaningless files on there (.iso files I had MD5 sums for), then pulled a drive from the array and formatted it in a different computer.

The array worked (albeit slower) with 3 drives. When I put the 4th drive back in, it was able to rebuild the array, but it took quite a while (several hours). all data verified okay by matching the md5 sums.

 

[Matthias99]

With a mirrored RAID level (all of them but RAID0), loss of a single drive will not ruin the array. You will be running in a "degraded" mode, generally, which reduces performance somewhat. Depending on the exact setup, loss of another drive at this point may destroy the array, losing some or all of your data, or it may be able to tolerate one (or more) additional failures.

You can recover the array by plugging in a new drive (which may require shutting down and restarting the system, but not with better controllers or if you have hot spares installed) and telling the RAID software to 'rebuild' the array (which takes from a few minutes to several hours, depending on the size and type of array and how much I/O is happening at the moment). Once the rebuild is complete, you're back to where you started.

I've never had a hard drive go bad in one of my personal systems, but I've seen it happen in servers with RAID, and I tested the RAID5 in my PVR after I set it up and it worked as advertised.

 

[D1gger]

Originally posted by: RudePuppy
... but I am just tired of backing up all my important bits. .....

Any RAID configuration is not a substitute for backing up your data. RAID can give you two copies of the file, so if one drive fails you have a backup copy, but if you overwrite a file by accident, or make an unintended change, it happens to both copies, there is no protection for user actions.

This is something that I learned from hard experience.

 

[bocamojo]

As others have described to some degree, there are different types of RAID solutions, which give you varying levels of redundancy / recoverability. RAID 1, or mirroring, makes a backup copy of everything. Therefore, if you lose one drive, in theory, you will have a perfect "mirror" copy on the other drive. Once you replace the failed drive, you can use the software to "rebuild" the mirror, or you can "break" the mirror, and just run on the single drive, thereby no longer running a RAID configuration. Also, in RAID 5, you are "striping" the data across multiple drives. The more drives you use to stripe, the more you can afford to lose. If you have a RAID 5 with 5 drives, for example, you could run in a degraded state with as many as 3 drives, and still be able to recover (once you replaced the failed drives and rebuilt the array). If you lose more than that, your array is gone, and your data is toast. Thus, even with RAID redundancy, you should always have a good backup of your data, if it is truly important to you. Most discussions of RAID on this forum are for performance purposes (RAID 0), and do not provide any type of redundancy, but rather improve write performance of the drives, which is good for gaming or for HTPC's.

Also, I have only run RAID 1 and RAID 5 (hardware RAID) on servers that I support at work, and they have saved a system from losing data more times than I can count. I have never run my home PC with these types of RAID. I use Ghost to image my systems at home, and it's fairly quick and easy to reload from these Ghost images, so that kind of defeats the purpose to me of running a RAID 1 or 5 configuration at home.

 

[imported_Mitchell]

I use Raid 5 and it has saved me a few times. Lost 3 drives over the course of 2 years and simply poped them out and put in a new on.

Hot swap drives FTW.