10th August 2007

Upgrading a RAID Array

posted in Hardware, Storage, Technology |

I’ve been giving some thought to upgrading one of my home RAID arrays lately. I currently have two 6-drive arrays attached to a single server via LSI MegaRAID SATA controller cards. One is using 250mb drives for 1.25gb capacity and the other is using 400gb drives for 2gb capacity. So far they have been operating fairly well.

While more capacity is nice, reliability is the most important thing. I bought that first array back in June 2004, which is just over 3 years ago. If I recall from the Google research on hard-drive reliability (ironic note- I couldn’t find the actual study with a quick Google, only lots of articles about it), age is one of the big factors towards failures, with lots of failures starting to happen when drives get to be about 3 years old.

So one question is about an upgrade process. I have lots of practice with simple usage of this array, at least enough to know not to pull multiple drives all at once. But to be honest I have not ever done anything complicated. Can I upgrade the drive size by just pulling the drives one at a time, replacing each with a bigger drive, waiting for it to rebuild until everything is balanced again?

Or is it much safer to copy everything somewhere else? This sounds like a pain since its 1TB, but then again with drive sizes now getting 1tb of free space somewhere else isn’t as hard as it used to be, just a bit slow.

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There are currently 5 responses to “Upgrading a RAID Array”

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  1. 1 On August 13th, 2007, Reeves Little said:

    Unfortunately, unless you’re using JBOD (just a bunch of disks, which you aren’t because your card doesn’t support it) you can’t add in disks of different sizes. The bad news is you’re in for either a laborious (lots of moving) or expensive (buying a new RAID card) switch.

    RAIDs work great when used as intended, but try to get fancy (breaking the RAID to split off disks, changing to a new protocol) and it’ll bite you. My recommendation: you need new drives, that’s a forgone expense, bite the bullet and get a new card at the same time and your data will be fully redundant during the migration.

  2. 2 On August 13th, 2007, Alex said:

    I’m not sure that is right- I’ve been reading the LSI card’s instructions and they are pretty clear that when a drive in the array fails it must be replaced by a drive the same size _or larger_. Now, presumably initially you don’t get to use the extra space, but once all the drives are new ones that are larger, in theory I should be able to set up a new “logical drive” on it. I just emailed their support to see if I can get an official word on whether this works.

    While poking around in their admin software I noticed that two of the older 250gb drives (#4 & #5) have a couple of media errors recorded. Sounds like motivation to take care of this sooner rather than later.

  3. 3 On August 21st, 2007, Anthony Pittarelli said:

    im having the same troubles with upgrading, my raid card can accept it, but i dont know how to repartition the drives to take advantage of the space when im done

  4. 4 On August 21st, 2007, Alex said:

    Since my last comment I asked LSI and they claimed it would not work, but the way their tech described it I think he didn’t understand and suspect it can work.

    The difficult part is that you can’t resize the disks. The MegaRaid will not support logical drives more than 2TB and its hard to resize an existing disk. But I should be able to add an extra logical disk and add it as a second volume. So I don’t get a full 4TB volume or anything (unless I do something like have Windows format it as JBOD) but I should be able to get a couple of smaller volumes.

  5. 5 On August 22nd, 2007, Reeves Little said:

    Yep, you can put in a larger drive… but it will be the same size as the other drives in the RAID.

    So, if your 250 gb drive fails and you put in a 500 gb drive you’ll have half the storage just sitting dormant.

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