Software mirroring - best way to replace a bad mirror drive?

Posted on 2007-07-27
Last Modified: 2010-04-20
I have a Windows 2000 SBS server with 4 Raptor SATA drives - 2-36 gig software mirrored as the C partition and 2-73 gig as the D drive. Event viewer is showing a bad block on drive 0 - the primary drive. I have an identical drive as the one that has the bad block.  Before doing anything I will Ghost the C partition onto an IDE drive. Once I have done that I am wondering what is the best way of replacing the drive with the bad block. Simply swap the good new drive for the bad old drive and boot up - will the orphaned remaining mirror automatically remirror to the new system - or do I have to do some prep work?
Question by:lineonecorp
    LVL 32

    Expert Comment

    I would be very careful about trying to use Ghost on a Raid-1 mirror, or even on a dynamic disl. See e.g.:
    It may be safer to not bother with Ghost. Just shut down the system (don't break mirror first), remove the failing disk, see if you can boot from the remaining good disk. You may need to move the good disk into the spot formerly occupied by the now failed disk.

    Go to disk management and you will see the removed failed disk showing up as "Missing". Right-click on that and select "Remove Mirror" and when that is done right-click on that same missing disk and select "Remove Disk". At this point you can shut down, install your replacement disk, restart, disk management, right-click on the system disk and select "Add Mirror" then point it to the new disk. The mirror should start rebuilding.

    The mirror will not rebuild automatically by just swapping in a new disk - you have to do most of the above steps.

    I am writing the above from memory so please treat that as an outline, and supplement with reading some docs on 2000 raid-1 mirror. e.g. you will not have the "Add Mirror" option if the replacement disk is even slightly smaller than the original, and it must be a dynamic disk etc.

    See e.g.:

    Author Comment

    Thanks for the super fast reply and info.

    1) As far as Ghosting the system, I read the tech note but I don't agree with it. I've Ghosted mirrored drives repeatedly and never had a problem. The Ghosted drive ends up being a basic drive and I throw it back into the system and boot up with it just to make sure it actually comes up.  It's never been a problem.

    2) The article you pointed me to is great.

    Minor issue 1: the article  is about 2003 which I don't think should be much different than 2000 - (?)

    Possibly more major issue: There is one item the article doesn't covercover - what to do about the mirrored D drives (data)  in the system while all the work with the C drives (system partition) is going on?  I've heard all kinds of urban legends about this - my preference has always been to boot up and do all the C stuff first and then simply reattach the D drives.  However, that's really a  superstition - it's not based on anything solid. The argument against it is that when the C drive boots without it's D, some 'pointers'/shares on the C that pointed to D might be disturbed/might have Exchange problems, etc. because the D drive is not there.   I've never really encountered those kinds of problems but I wouldn't mind being pointed to something more definitive on the 'right' way to do this.

    One additional preventative procedure I would recommend is to make an FT boot diskette prior to doing anything.  It's saved me a few times.

    Thanks in advance.
    LVL 32

    Accepted Solution

    (1) OK, if you've done it before then I see no problem. Just did not want to take the risk if this was the first time doing it.

    (2) Re. 2003 vs 2000 there should be no real difference. I used software mirror on both and the only difference is minor terminology (e.g. "rebuilding" on 2000 is called "resynching" on 2003). MS used to have a very nice article on software mirror in 2000 but it seems they've removed all those articles now they're no longer supporting 2000, seems senseless to me.

    Re. the D: drive I would vote for leaving it in place while doing the other stuff. As long as you don't get the drives mixed up with each other in Disk Management there is no downside. In this case they are different sizes so risk of mixups is very small.

    Yes, good point about the boot diskette.

    If you've trouble booting from the remaining good mirror disk you may have to put in the position where the failed disk used to be.

    Good luck.

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