How do I replace both drives in a RAID 1 configuration?
February 20, 2011 11:26 AM   Subscribe

How do I replace both drives in a RAID 1 configuration?

I have a 2 ½ year old Dell XPS with 2 mirrored 500MB drives in a RAID 1 configuration.

A year or so ago 1 of the drives in the set died, but my system remained stable because of the RAID, then over the last few months I seem to be having repeated hardware errors causing blue screens of death (typically siting MEMORY_MANAGEMENT as the cause) and now increasingly files on the remaining drive are becoming corrupt. When I ran a memory diagnostic it said there was a memory error.

I desperately want to protect my data (I've recently found by accident that a number of files of my PhD data have become corrupt, and I've backed up the corrupted files and overwritten my backups!)

The set up is a Dell XPS 420, Intel Core 2 Quad CPU ~ 2.4 GHz, RAM 4GB running Vista Home Premium SP1 (I can't get it to upgrade to SP2 for some reason).

Googling has found lots of sites telling me how to replace a single hard drive but not how to do this with a RAID configuration replacing both drives...

Thank you in advance!
posted by inbetweener to Computers & Internet (7 answers total) 1 user marked this as a favorite
The whole point of the system is that when one drive goes bad, you replace it, data from the good drive is copied across to the new, functional but blank disk, and then you have two good copies again. You can repeat this indefinitely and always have good data. If you wait for them both to fail, you're basically in the same place as if you've had two non-RAID drives fail on you.

If both disks are still sort of functional and you can get some of the data off each, then you can hope that no bad spots on each disk overlap, and try to copy the good parts off each disk, but I don't know an easy piece of software to do this. Conceptually, I'd do the following: Copy all data off of drive 1, and note failures for specific files. For the noted failures, go back and copy the same files off disk 2, hope none of them overlap. Maybe there's a piece of software that can do this for you, but I don't know it. A script to do it shouldn't be that hard to write.
posted by tylerkaraszewski at 11:35 AM on February 20, 2011

Best answer: I'd probably buy a new external drive and copy what you can to it. Replace the two drives with brand new ones and configure it as a RAID. Then copy the files back from the external.

Unless I'm misunderstanding, you technically no longer had a RAID as soon as the first drive died. You just have a glitchy drive.
posted by sharkfu at 11:38 AM on February 20, 2011

If you think your RAM is bad you should boot from a memtest86 CD and test it one DIMM at a time.
posted by thewalrus at 11:51 AM on February 20, 2011

Oh and "Can't get it to update to SP2 for some reason" seems more like a Windows specific OS corruption issue than a problem with hardware. Some key piece of Windows is broken.
posted by thewalrus at 11:52 AM on February 20, 2011

Get into whatever RAID management config is on your system during bootup and remove the mirroring relationship so that you now have two drives that are identified as separate by the system.

As sharkfu says, it sounds like you no longer have a RAID setup: you have a broken array and a glitchy drive, and you just need to offload/salvage what you can, and replace them both. Or just get one big drive for the system, and two more to do what jwz says, because RAID is not backup, and you haven't really used the RAID 1 the way it's meant to be used.
posted by holgate at 11:53 AM on February 20, 2011

Best answer: Your corruption is, I'd bet, less likely due to failing drives than to improper shutdowns. However, it can't be stressed enough: you need to reinstate a RAID to store your data, and copy over what you can. There are three steps to focus on:
  1. Getting a DAS device for your data
  2. Migrating your data
  3. Backing up externally
1. Getting a DAS device for your data
First, I'd suggest you not try to replace the drives- they are likely more cheaply replaced with larger models anyway, and I'll be honest: if you didn't know enough to replace the RAID drive for a whole year when it first failed, I'd be concerned about your technical chops to swap in a valid new drive and rebuild successfully. No offense intended, of course, but it may be safe for you to copy the files over to a shiny new location than to take a chance of losing everything when you set up the RAID mirror incorrectly, etc. The worst case of copying files is you re-copy them if anything goes wrong.

I'd suggest getting an inexpensive direct attached storage (DAS) RAID enclosure and two large drives to start. With a RAID enclosure, your computer sees it as a simple attached drive, while the case itself contains 2 or more drives and had has hardware RAID built-in; this has the advantage that even if you wipe your OS completely- or connect it to a new machine- the drive is untouched with all its data.

The enclosure itself will run in typically 2 or 4 bay models, ranging from under $100 to $400 or more. You don't need much, so probably a simple 2-bay system will suffice; a quick search on NewEgg turns up plenty of simple RAID enclosures with 2-bays in the $70-150 range, but you should look around; key elements are supported drive size, supported RAID types, and OS compatibility/software. On top of that you'll have to buy two drives- but drives are so cheap that a 500GB SATA drive will run ~$40. Hardware wise, you can come in at as little as $200, depending on your space and feature needs.

I don't know how much of a price difference computer shopping in the UK makes, however. If you link to an online computer store that services London (and/or has brick and mortar storefronts) I or these other posters can certainly help you pick out a winner.

2. Migrating the data
Once you have the DAS/NAS set up, you'll want to copy the data. First, I'd start by copying the data directly from your current OS, as it is now. That'll get you ~95-99% of your data, or basically whatever you have today. Then, I'd follow tylerkaraszewski's suggestion and try to 'break' the RAID (it wasn't clear if this RAID is in the hardware, or defined in Vista using software RAID) so that you have two separate drives: one the dead one that isn't apparently working, and one the active drive that you just copied data from. If the bad drive is somehow accessible, you can manually compare the corrupted files with what's on the bad drive, and see if that data is preferably, and hand-copy the individual files over. Otherwise, you're just saying "Well, let's protect what I have left". Toss the dead drive and be done with it.

Now, of course, you'll want to make sure you keep that new enclosure in top shape; it's not a horrible idea, at $40 or so, to have bought a third hard drive that you keep tucked away and still in its packaging, so that if one of the drives fails in a year or two, you have a spare already at hand. A sealed drive should last on a shelf for a good long while.

3. Backing up externally
Lastly, especially if you have mission critical data on there- such as PhD content- you absolutely have to not only replace your RAID, you have to find an offline backup source. This means a backup to a location outside of your physical residence. If your dog peed on your DAS, or your home went up in a fire tomorrow, even that shiny new RAID would be worthless, right?

The external backup is something that can be done once every 1-2 weeks, and you set up. Options can include (with a little elbow grease) simply finding another person to have mutual backups with, or going with a paid online storage solution. A lot will depend on the size of your data, the importance of keeping it secure, the ease of access, the frequency of backups, etc. If you're interested in this- and you should be- you can ask more questions on this thread and we can help you out with possible online backup options.
posted by hincandenza at 5:57 PM on February 20, 2011

Response by poster: Thank you all. I realise I was being pretty damn stupid not having replaced the drive immediately. I won't make the mistake again. I've now replaced both hard drives, reinstalled Windows, reset up the RAID, set up offline backup with Mozy and managed to rescue almost all of my files.

Unfortunately, this is likely to recur as I'm still having improper shutdowns as the computer is, despite all the above, still bluescreening quoting memory management errors... but that would be the subject of a new question.
posted by inbetweener at 1:25 PM on March 3, 2011

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