jk's blog

Upgrading to a Larger Hard Disk, using Windows Software RAID 1 Mirroring

Technically, you can’t extend a mirrored volume, but you can break the mirror and extend it. Then, you can re-build the mirror.

Here’s how to upgrade to a larger disk, using mirroring to copy the data over. I’m going to assume you want to go from a single disk to two larger disks: a spare disk is cheaper than dealing with hours of disk recovery in the event of a crash, no matter how rare crashes are.

Start by making a full backup of your disk to an external drive.

Install one new disk and making a mirror onto it.

Then, remove the boot disk, and see if it’ll boot off the second disk (aka, second plex). If that works, great. Reboot.

Add the second new disk. Go into Disk Management. It’ll ask to initialize the new disk – choose whatever works, probably MBR.

Then, delete the missing volume (the disk you removed). It’ll still show up in Disk Managment, but that’s just the data about the missing disk. Deleting it breaks the mirror.

Then, re-establish a new mirror. I don’t think this is strictly necessary, but it’ll only take an hour or two, and it’ll create another copy of your data. (When this is done, you’ll have three copies of your data.)

Next, break the set by unplugging the second disk (aka, Disk 1, or whatever is on the second SATA port). Boot, and then go into Disk Management and remove the missing disk from the list.

Now, that disk is no longer in a mirror, so you can extend the partition.

Shut down, plug the second disk back in, and then boot.

Back in Disk Management, you can now see the new disk, and it won’t be working. Reactivate it so it’s empty, and then make a mirror for the C: volume. (When you reactivate, don’t do anything to restore the data from it.)

Finally, go into the Computer -> Properties -> Advanced Settings -> Startup and Recovery… and select the second-to-last plex to boot. (The ones before it were created each time you mirrored the disk.)

There you go. It’s a lot of steps, but you can use the computer between reboots. So the impact is only a half hour to an hour, not the half-day that a USB disk backup and restore would take.

Removing the nonfunctional plexes

Your mirrored disks are the last two plexes on the boot loader’s menu. You can remove the invalid entries with the “BCDEdit” too. You run a shell as administrator, and type “bcdedit” to get a list of the boot options. Then enter a command like this, using the appropriate identifier. This is in PowerShell:

bcdedit /delete "{832abe23-40f2-11e0-b869-89f15cc42e86}"

The quotes protect the braces from interpretation.

If you’re uptight about the name of the plex, you can rename it like this:

bcdedit /set description "Windows 7"

Run “bcdedit /? set” for help on the set command.