by Greg
Tue, January 10 2012 09:58
Unless you are using a solid hardware mirror, which unfortunately does not come standard on today's motherboards, Windows 7 drive mirroring is a viable option if you want a certain level of fail-safe redundancy. Backups are always you best bet for redundancy.
Breaking drive mirrors in Windows 7 is very simple. Go into Disk Management, right click on a disk in the volume, and select "Break mirror". You are back to two identical disks.
If you are going to remove one of the disks and if your user profiles are located on these disks, you have to be very, very careful with your next step. You now have two identical drives with their own copy of the user profile.
Shut down the computer right away to remove the drive. The trick is to ensure the remaining drive is the lower of the two SATA drive channels. For example, if your array was on SATA3 and SATA4 mapped to D:\, once the array is broken Windows will automagically assign D: to the SATA3 drive and E: to SATA4 drive. If you remove the SATA3 drive, Windows will not be able to find the user profile on E:... because there is no D:. Worse yet, by attemping to log in you have now corrupted the registry and will start receiving error messages like "The user profile service failed the logon. User profile cannot be loaded."
If, however, like me you learned this after the fact there is a relatively easy fix in this KB article:
http://support.microsoft.com/kb/947215
Basically you have to restart the computer in safe mode and make changes to the registry. Because Windows is in a wonky state you will need to run regedit directly from the C:\windows folder. From there, follow the instructions in the kb article and you should be good to go.