I'm attempting to use software mirroring to move the system partition between different hardware raid arrays. Unfortunately, whenever I pull the primary disk offline, I'm not able to get the boot loader to choose the Secondary Plex. How can I make the secondary plex bootable without the primary online?

Disk Type(s): Dynamic
Partition Style: MBR

Any assistance is appreciated, thank you.

  • How do you mean primary and secondary?? – Chopper3 Nov 20 '10 at 21:30
  • Well, the actual disk/array that the OS was originally installed to is considered the primary plex - whereas the disk/array that I added as a mirror is referred to as the secondary plex. When the primary plex is offline, it appears the bootloader doesn't function. – CurtM Nov 20 '10 at 21:32
  • DISKPART is supposed to add a boot-option for booting off of the 2nd plex. Is that missing? – sysadmin1138 Dec 1 '10 at 0:01
  • As soon as the first plex is offline I never get a screen to choose the second plex. It acts like the second plex isn't bootable at all. – CurtM Dec 1 '10 at 0:04

After encountering the limits of software RAID in w2k3 we moved to hardware RAID. Have not tried in in W2K8. IIRC the problem we found is the software raid is only for 'data protection', according to the KB article. The second disk will not for boot by itself, you had to jump through some loops with boot records.

We get good off lease/used RAID cards cheaply, only get the well known names. Hardware raid will do it properly and support hot swapping. Software raid was just too hard.


Are you removing the old controller? If you aren't keeping it around, you wouldn't try to boot from the "secondary plex" at all - it would become the primary in that case.

After mirroring completes - what happens if you "break" the mirror and return the drive back to a dynamic or simple volume?

  • There's 1 raid controller and 2 hardware based arrays. – CurtM Dec 3 '10 at 4:16

Based on the the description so far this is what I assume you have: Windows OS. 2 raid cards with one disk on each card.

Most likely the problem is in the BIOS it is set to read the first raid controller. You either need to move the disk over to the other controller (only if they are the same card) or change which raid card is used to boot from.

  • There's 1 raid controller and 2 hardware based arrays. – CurtM Dec 8 '10 at 4:23

This is software RAID -- it's not bootable. If you want to make the secondary drive bootable, you can do that, but the software RAID has nothing whatsoever do with that process. (The software RAID just keeps the data on the two drives in synch and allows the filesystem to recover with just one drive.)


Admittedly this is a stab in the dark as I haven't had to do this before. That said...

Have you tried placing the secondary RAID controller in the same slot as the first when disconnecting the primary? The physical placement of drives within the server do matter for the bootloader, which may cause issues.

  • There's 1 raid controller and 2 hardware based arrays. – CurtM Dec 3 '10 at 0:55

You can try with modifying boot sequence and add secondary plex. You can check following URL if that would help


  • 1
    The instructions linked in the article relate to Server 2003 - the boot loader was changed significantly in Server 2008. – CurtM Dec 8 '10 at 4:24

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