Simple (OS) and Mirrored Volumes on Same Drive - Problems?
My system is configured with two 1TB drives which are are formatted as Dynamic drives. I understand that Win 7 does not officially support mirroring on the OS partion so the C partition is formatted as a
simple volume (200GB) on Disk 0 and the Data partition is Mirrored
(731GB) on disks 0 and 1. That leaves 200GB of unformatted space on the second disk (disk 1). I have prepared a backup of the OS on a USB drive in case of failure of Disk 0.
OK, so if disk 1 fails I install a new disk and the data partition's mirror will automatically rebuild and I'll be back where I started.
My question is what happens if disk 0 fails? Do I just boot off of the Win 7 CD, restore the OS backup to the unallocated 200GB of space on disk 1 and then install a second disk which will then automatically rebuild the data partition's mirror? Or is this
configuration unworkable in recovery mode if disk 0 fails?
May 11th, 2011 9:55am
steveoman wrote:
My system is configured with two 1TB drives which are are formatted
as Dynamic drives. I understand that Win 7 does not officially
support mirroring on the OS partion so the C partition is formatted
as a/simple volume/ (200GB) on Disk 0 and the Data partition is
Mirrored (731GB) on disks 0 and 1. That leaves 200GB of unformatted
space on the second disk (disk 1). I have prepared a backup of the OS
on a USB drive in case of failure of Disk 0.
OK, so if disk 1 fails I install a new disk and the data partition's
mirror will automatically rebuild and I'll be back where I started.
My question is what happens if disk 0 fails? Do I just boot off of
the Win 7 CD, restore the OS backup to the unallocated 200GB of space
on disk 1 and then install a second disk which will then
automatically rebuild the data partition's mirror? Or is this
configuration unworkable in recovery mode if disk 0 fails?
Who told you, that Win7 does not support mirroring of the OS partition?
I have setup one. It's really easy, and afterwards you can choose on
every startup, from which drive you want to start the OS.
Wolfgang
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May 11th, 2011 6:48pm
Who told you, that Win7 does not support mirroring of the OS partition?
I have setup one. It's really easy, and afterwards you can choose on
every startup, from which drive you want to start the OS.
Wolfgang
I read several articles on other forums saying that it does not work (or is not supported) and that the OS is not bootable if disk 0 fails, which renders it rather pointless. I have read of several others (including you) who say that it does work so maybe
it's unreliable or inconsistent. It does sound a bit strange that it offers you a choice at boot though, as if it sees both drives as independent OS installations (multiboot) rather than a single mirrored OS.
When you say that you can choose on every startup does that mean that you always get the choice and that it waits at a prompt until you choose or does it start booting from the default disk after a few seconds wait? Or can the option be switched off and
boot automatically from the default drive?
May 12th, 2011 5:39am
Who told you, that Win7 does not support mirroring of the OS partition?
I have setup one. It's really easy, and afterwards you can choose on
every startup, from which drive you want to start the OS.
Wolfgang
I read several articles on other forums saying that it does not work (or is not supported) and that the OS is not bootable if disk 0 fails, which renders it rather pointless. I have read of several others (including you) who say that it does work so maybe
it's unreliable or inconsistent. It does sound a bit strange that it offers you a choice at boot though, as if it sees both drives as independent OS installations (multiboot) rather than a single mirrored OS.
When you say that you can choose on every startup does that mean that you always get the choice and that it waits at a prompt until you choose or does it start booting from the default disk after a few seconds wait? Or can the option be switched off and
boot automatically from the default drive?
Edit: Here is one comment I found in another forum regarding disk 0 failure on a mirrored boot disk: "I had no problems mirroring C: either. And I did have the main disk of C: fail and Windows 7 did keep right on running until reboot. Now, in order to
reboot, I had to then scroll down and pick the boot entry for the other disk (Secondary Plex) to boot back up. Disk Management showed C: but in failed redundancy. I got a replacement disk and installed it. I had to break the mirror by right clicking on the
Mirror Volume C: (not the physical Disk 1) and “Remove Mirror”. Now I could add a mirror back to C: and picked the new Disk 0. After resync it showed healthly. But, with ONE caveat. For whatever reason, it did NOT rewrite the boot sector to the
replaced Disk 0. When rebooting, when I pick the original boot entry for Disl 0 (the default) it does not boot or even display boot menu. So, the mirror rebuild did not apparently add back the boot sector. I could still boot the Disk 1 (Secondary Plex)."
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May 12th, 2011 5:40am
steveoman wrote:
Who told you, that Win7 does not support mirroring of the OS
partition? I have setup one. It's really easy, and afterwards you can choose
on every startup, from which drive you want to start the OS.
Wolfgang
I read several articles on other forums saying that it does not work
(or is not supported) and that the OS is not bootable if disk 0
fails, which renders it rather pointless. I have read of several
others (including you) who say that it does work so maybe it's
unreliable or inconsistent. It does sound a bit strange that it
offers you a choice at boot though, as if it sees both drives as
independent OS installations (multiboot) rather than a single
mirrored OS.
When you say that you can choose on every startup does that mean that
you always get the choice and that it waits at a prompt until you
choose or does it start booting from the default disk after a few
seconds wait?
The later, if you don't choose within a configurable timeframe it
starts the default partition.
Or can the option be switched off and boot
automatically from the default drive?
Edit: Here is one comment I found in another forum regarding disk 0
failure on a mirrored boot disk: /"I had no problems mirroring C:
either. And I did have the main disk of C: fail and Windows 7 did
keep right on running until reboot. Now, in order to reboot, I had to
then scroll down and pick the boot entry for the other disk
(Secondary Plex) to boot back up. Disk Management showed C: but in
failed redundancy. I got a replacement disk and installed it. I had
to break the mirror by right clicking on the Mirror Volume C: (not
the physical Disk 1) and Remove Mirror. Now I could add a mirror
back to C: and picked the new Disk 0. After resync it showed
healthly. But, with ONE caveat. For whatever reason, it did NOT
rewrite the boot sector to the replaced Disk 0. When rebooting, when
I pick the original boot entry for Disl 0 (the default) it does not
boot or even display boot menu. So, the mirror rebuild did not
apparently add back the boot sector. I could still boot the Disk 1
(Secondary Plex)."/
That would not really worry me because it's not a big problem to add a
bootsector back to an installation. As long as the whole disk is there,
you can boot via a repair or install disk and readd the bootsector. And
it's always a little bit more work to repair a software raid as opposed
to a hot-plug hardware raid, where you just switch drives without even
shutting down your machine. But if the systew is able to switch
transparently from one drive to the other on failures, without
interrupting operation, that is much more security than your hand-made
workaround can offer.
Wolfgang
May 12th, 2011 9:02am
Wolfgang,
Thanks for the answers. I agree that it's better than my somewhat fiddly solution, which I think would not have worked anyway (see my comment regarding the boot sector below), so I've gone ahead and done it and so far it seems ok; I can now boot off of either
disk and I have set the time to automatically boot from the default drive to 10 seconds. The only annoying thing is that I had to remove the mirror from the data partition in order to add the mirror to the system partition, which I suspect has probably got
something to do with the boot sector. Now resynching the data disk mirror.
Steve.
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May 12th, 2011 9:14am