Raid5 drive rebuild

Posted on 2011-11-01
Last Modified: 2012-08-13
We have a Dell 6800 server running windows 2003 standard.  The raid5 has a perc4DI controller and recently one of the drives drive 0:0 failed and the server is running off the remaining 3 drives.  The problem is few days ago the drive 0:1 went into predictive fail mode and is still online so we ordered 2 replacement drives.  I spoke with 2 dell techs that said as long as server is up and running, once replacement drives arrive, i could replace drive 0:0 first and run a rebuild.  They both said it was ok to run a drive consistency check on the drive after the rebuild.  Problem was yesterday after i ran the rebuild which completed to 100%, overnight this new drive went into predictive fail mode as well.  My question is, shouldnt i have tried repairing drive 0:1 first by running a drive consistency check on it so that when the new drive attempted the rebuild it wouldnt take bad portions from the predictive drive 0:1?  Was told by a 3rd tech today that my only option is to go into bios and try retagging array and then taking drive 0:1 offline then replacing drive 0:0 with new 2nd drive which i didnt use yet from yesterday and there would be a 50% chance this would work without having to rebuild the server.  Didnt sound very promising.  My idea was to use the 2nd new drive to replace the first new drive that was rebuilt since its not in good condition now and then rebuild it after running drive consistency check on predictive drive 0:1 first.  I always thought that in a raid5, as long as server is up and running and you still had 2 good drives online, that you could recover without rebuilding server.  Thanks.
Question by:dankyle67
    LVL 20

    Accepted Solution

    personally - i would make a backup immediately - useing a disk image program like acronis or storage craft - that way if you have to rebuild the raid from scratch you can readily restore.

    raid 5 - typically you can only lose one drive - you must have at least the number of drives required to add up to the capacity of the raid array.
    4 x 1Tb drives in raid 5 - would give 3tb space - so you must have 3 drives working to have 3tb of data
    if you had raid 10 - you would have 4 x 1tb drives giving 2tb of space - you could lose 2 drives - but they are paired - so you couldnt lose one pair
    LVL 6

    Assisted Solution


    I had this problem so many times with Dell Servers.
    Before doing any thing try to Clone your server or do a backup.
    first of all you need to go into your PErc 4i Configuration Interface, i think "ctrl+A" .
    then you need to take all of your disks to Offline Mode, Go to virtualization as i remember and you'll find import, you need to import the configuration first.
    after that you'll have rebuild, rebuild the Raid 5 disks.
    after you finish, restart your server and everything will work fine.
    But like i said before doing any thing, Backup.

    Let us know, Thanks.
    LVL 8

    Expert Comment

    I agree with the previous answers as I also strongly suggest clone your existing system and play safe. Make a couple of full clone of your HDD in different medias or locations the even you may start from the scratch building your RAID and replace all HDD in one time.

    Author Comment

    Yes will do an image of c drive using Bootitng and then will try going doing the Ctrl A as advised and import the configuration of the raid5 then rebuild.  Will this work when we have 2 predictive drives already degraded and 2 good disks online for total of 4 disks in the raid5?
    LVL 8

    Expert Comment

    Play in safe side get full clone image of your system because if you loose RAID you willall partitions!
    Since your are using RAID5 with 4 disks, its better rebuild them by adding one HDD each time not 2 of them in same time! Adding 2 HDDs means you remove 2 HDDs and RAID5 with 4 HDD cannot survive when you remove 2 HDDs!
    LVL 14

    Assisted Solution

    You cannot run a consistency check on an array that is degraded, so this is why they told you to try and rebuild and then run it.

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