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I've been looking to set up a pair of RAID-1 (mirrored) drives for data archiving. My first reaction was to just go out and get an enclosure with 2 drive bays and a built-in RAID-1 controller. After a bit of research, I saw it mentioned (wish I still had the link) that if a hardware RAID controller fails, it usually means the data is unrecoverable, except with a similar controller by the same manufacturer.

Software RAID seemed like a good solution to that problem, except I imagine it would not be a good idea to try to access the data from an operating system that did not create the RAID volumes (I have a dual-boot machine, Linux/WinXP) - I'm guessing the creating OS would think the two volumes are out of sync and then have to spend lots of time resychronizing. I wasn't too concerned with performance issues of software vs. hardware because I don't access most of this data on a very regular basis (much of it is digital media, and most days I don't see myself accessing more than a dozen files out of many).

So the questions:

  1. Just how serious is it if a hardware RAID controller fails? Am I really stuck with going back to the manufacturer for recovery? A lot of the vendors seem like small companies, if something fails in a few years and the vendor is gone, is my data gone as well, or are there other ways to recover? Is there no standard for these things that multiple vendors stick to (or is that just wishful thinking)?

  2. Is there any concievable way to get a software RAID usable across multiple OS's? I'm probably upgrading to Windows 7 in the next 6 months, and I still have the linux system which I'd like to use to access the files as well as on windows. I suspect the answer will be "no", but still, just thought I should ask...

EDIT: Now that I'm fully awake and have had some coffee, I realize the second question is a little silly. Please feel free to ignore it (but not deleting it because some have already tried to answer it).

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3 Answers 3

up vote 2 down vote accepted

It's a little tricky to answer this explicitly, mainly because many off-the-shelf RAID1 products are in fact just using software RAID themselves with a simple SATA backplane for connecting the drives.

Most of your SOHO RAID1 solutions will be using a Linux mdadm software raid setup and so long as the device allows you to choose your file system type you'll be able to chuck the HDD into any system and read the data back from it. i.e., you will not need a new NAS to read your data again. QNAP boxes give you the choice (this is what I have) but I have read that Netgears use their own propitiatory file system. I cannot vouch for other manufacturers.

So just make sure you know what you are actually buying. An off the shelf RAID1 NAS does not mean a hardware raid controller.

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Thanks, I'll look into QNAP, now that I've got a name to look for. :) –  FrustratedWithFormsDesigner Sep 17 '10 at 17:26

For your first question - for Raid 1 mirror, it shouldn't matter. Most of the controllers I have seen store the data in a normal fashion, just that it automatically sends it to the second drive at the same time. You should be able to pull any single drive out and plug it into another controller. For any other Raid level - usually you must have the identical controller. YMMV and I'd make sure to check with the documentation from the manufacturer.

For your second question - think about this - the software Raid is controlled by the OS running at the moment - so the Windows partition would only be raided while Windows is running. The Linux would be raiding its partition while it is running. Both OS can't be running at the same time and raiding their own as well as as the other partition since the competing OS wouldn't allow it.

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Thanks, I had gotten the impression that RAID-1 would be controller dependent, but I'll remember to check the specs first. –  FrustratedWithFormsDesigner Sep 17 '10 at 13:24

1) Serious. Very likely stuck since you can't just switch over to software raid or stick drives as is into a new box that doesn't have exactly (or nearly exact) same raid1 controller.

2) My gut feeling is this is "too hard" if you want the data available to both systems. Software RAID1 for windows will want to be NTFS and RAID1 for Linux will want to be ext#.

You might want to think about an NAS solution if you have a fast local network available. You can put both the drives in the NAS and get to them from either Windows or Linux over the network. In my case the "NAS" is a box running FreeBSD 7.1 and Samba. FreeBSD RAID1 is relatively easy but there are other NAS solutions where all you do is plug in the drives and attach an ethernet cable.

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A separate NAS would work - I looked at a couple at one point. They were the second kind you mention: plug in the drives and network and you're done! Do you know of any that have built-in software controllers, to avoid the problems of failed hardware controllers? –  FrustratedWithFormsDesigner Sep 17 '10 at 13:27
    
@Frustrated...: Because I chose the Do-It-Yourself NAS solution I'm not familiar with the details of others. My guess is that most will have hardware controllers since that does simplify the problem from the vendor's point of view. It also locks you into their solution set (which is a bonus from their perspective). –  hotei Sep 17 '10 at 14:16
    
Well, that sounds like a good project for a long cold winter. :) I don't have a spare machine right now, but if I can get one (or get the parts) I'll look into that. –  FrustratedWithFormsDesigner Sep 17 '10 at 14:44

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