Rebuilding RAID 5 disk array ?

Posted on 2005-04-08
Last Modified: 2010-04-03
I have a 4 x 200 GB SATA RAID 5 disk array  with only  20%  used space.  Today one disk  failed and I took it out.

Is it safe to continue running this disk system with only 3 disks? Is there enough data redundancy to allow for another disk failure? Should I rebuild the  3 disk array now? Obviously, the failed disk will be replaced, but that might take some time.

The array is part of  a Red Hat 9 Linux  data server.
Question by:eruskov
    LVL 95

    Accepted Solution

    RAID 5 allows for a MAXIMUM of ONE disk to fail.  If you have a failed drive already, then another failure and you lose ALL YOUR DATA.  Of course, rebuild it NOW.  Go to CompUSA, MicroCenter, or whatever your local computer store is and get a new drive NOW.

    RAID 5 spreads the data over all disks in the RAID so in a sense, each disk in your 4 disk RAID 5 is 7% used; with one disk worth of space (not one physical disk) used for parity.  

    In addition, your RAID drive is now operating slower as the controller has to reconstruct the data that it would normally be reading from the missing drive.
    LVL 7

    Assisted Solution

    what leew said times ten,
    don't risk your data
    LVL 87

    Assisted Solution

    It depends on how your raid has been setup. often you have 3 disks raided and an online spare. When one of the raided disks breaks down, the online spare should automatically take over the funtions of your failed drive. Once the array has been rebuilt to that online spare, another drive can go to nirwana. If all your drives are an active part of your array you must replace the bad drive with a good one and wait for the array to have been rebuilt before you can shoot another drive.

    I don't know your array, was it built with online spare or not?

    Author Comment

    Thanks for the quick replies and advice!

    I have a Relion Xeon 2U Servers from Penguin Computers and it came with the 4 x 200 GB SATA RAID 5 disk array that I mentioned above.

    Today I bought two 200Gb Maxtor SATA drives and one of them is currently being rebuilt as part of the RAID array. There is one disk slot left and I would like to use it as an online spare. How do I do that?  

    Any comments about  mixing disk sizes in a RAID arrays?


    Author Comment

    Ok, I guess my last comments merit a separate question. I am closing this question and  splitting the points.
    LVL 87

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