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  • Can't break mirror?

    I've got a 2008R2 server running off a software mirror from two disks. There's a parallel install (or was) install on the 1st partition, mounted as C:. The running OS is on the 2nd partition, mounted as D:. This was working fine. In the past with w2k and 2003 servers I could simply break the mirror and reboot. No so with 2008R2. When I try it complains about the plex being part of the boot or system. STFW brought up an MS note suggesting use of an elevated cmd prompt and the diskpart program. Tried that, same error! WTF?

    What I'm after here, is to move everything off these two software mirrored drives and onto a 4 drive hardware RAID5. The OS has the drivers loaded already (jmicron). I've tested it by creating a RAID5 and it comes up in the OS just fine. Anyway.

    But in order to get the machine state backed up properly (more importantly, restored) I've got to ditch the mirror. I can't reload a bare metal or system state unless it sees two 'drives' on which to recreate the software mirror. Trust me, I've tried. A bare metal backup refused to use the single (and much larger than before) RAID5 volume. Same deal with one with the system state. I would've preferred to avoid going the whole reinstall the OS route.

    So what's the deal? How do I get the mirror broken? Can I safely break it using just the setup DVD? Or via booting into a parallel OS?

    Help!

  • #2
    Re: Can't break mirror?

    This is Windows mirroring rather than an onboard RAID controller, I presume?

    Why not just unplug one drive and let Win2008 handle it as "failed"
    Tom Jones
    MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
    PhD, MSc, FIAP, MIITT
    IT Trainer / Consultant
    Ossian Ltd
    Scotland

    ** Remember to give credit where credit is due and leave reputation points where appropriate **

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    • #3
      Re: Can't break mirror?

      Yes, it's running on a software mirror now. I'm interested in moving it to a hardware RAID5. Thus far I've discovered you cannot restore a bare metal backup onto a different drive setup. As in, if it was software mirrored before it has to set itself up that way again.

      I try to avoid forcing the issues when it comes to RAID configurations. I've had bad experiences in the past with partitions getting lost in the process. I'd like to avoid rebuilding the whole server setup again.

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      • #4
        Re: Can't break mirror?

        You should just be able to run command prompt as administrator and run the following command -
        DISKPART>break nokeep disk=2 (where 2 is the secondary plex)

        This will break the mirror and remove data from the drive.

        Once done, use something like Acronis to perform a bare metal image, install the RAID
        card and set up your RAID 5.

        Then perform a bare metal recovery to your new RAID 5.

        for the price of a disk though, don't use your good disk in the RAID set as you can always go back
        to it in (just in case)

        Ste
        Steven Roberts
        IT Mercenary

        MCITP:EA|MCTS|MCSE 2003 (Messaging and Security)|MCSA 2003 (Messaging and Security)|MCP|Prince2 Practitioner

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        • #5
          Re: Can't break mirror?

          diskpart cannot break it. It's in use and neither the GUI nor diskpart will break it. It used to be able to do this, but not on the 2008R2 install I've got running right in front of me.

          Nor can you do a bare metal restore to the array. Bare metal backup of a software mirror insists on restoring onto the same number of drives. Thus the reason I wanted to break the mirror. I wanted to break it, do a bare metal backup of the single drive setup and then do a restore onto the single drive array. But I can't do that until I get the mirror broken.

          Apparently the only way to break this mirror would be to reboot without the mirrored drive. That would, supposedly, then allow using diskpart to break it, using the m prefix notation on the missing drive. I've had bad luck in the past with forcing mirror issues, thus my hesitation.

          Instead I'm redesigning the setup and use a pair of mirrored SSDs for the OS and putting the data on the array. I can't use just the array because of the greater than 2TB size of the array. When a drive is larger than 2tb the OS can't be installed unless the motherboard can boot from EFI (instead of BIOS). Few motherboards do this.

          I suppose if the RAID hardware supported creating separate volumes I could do it. But the one I've got doesn't. It just maps all the drives together as one volume (although I may go back an re-check this) If it did I'd set up the array to create two volumes, one with MBR and small enough for the OS restrictions, and then the rest as GPT. That way the OS could boot into the sub-2TB-sized partition and then mount the larger one as GPT.

          Hopefully others will stumble across this message thread and save themselves the hassles I've gone through discovering what won't work.

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          • #6
            Re: Can't break mirror?

            Originally posted by wkearney99 View Post
            I've had bad luck in the past with forcing mirror issues, thus my hesitation.
            7 years, presumably

            I've always found software mirroring is a pain in the butt, good in training courses but useless in real life.

            Removing one drive will break the mirror and give you a back up copy so you should be relatively risk free
            Tom Jones
            MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
            PhD, MSc, FIAP, MIITT
            IT Trainer / Consultant
            Ossian Ltd
            Scotland

            ** Remember to give credit where credit is due and leave reputation points where appropriate **

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