1. Basic disks use the original MS-DOS-style master boot record (MBR) partition tables to store primary and logical disk partitioning information. Dynamic disks use a private region of the disk to maintain a Logical Disk Manager (LDM) database. The LDM database contains volume types, offsets, memberships, and drive letters of each volume. The LDM database is also replicated, so each dynamic disk knows about every other dynamic disk configuration. Performing FIXBOOT and FIXMBR in the recovery console of a system configured with Dynamic disks has no affect on the health of the LDM.
  2. Never break a healthy system disk or boot dynamic mirrored volume and expect the mirrored drive to replace the original primary drive if it fails. The manually broken mirrored drive is assigned the next available drive letter, and this is updated to the permanent record in the LDM database. This means that regardless of what position that drive takes in the boot process, it is assigned the new (and incorrect) drive letter, so the operating system cannot function correctly.
  3. If you want to replace a failed disk in a dynamic disk-based volume, shut the system down just like normal. Do not break the mirror or change the volume properties in preparation for the removal. Once the system is down, replace the bad drive and reboot. It may be necessary to place the secondary drive at the same SCSI ID as the primary before reboot if you are replacing the primary drive in a mirrored set.

MANY other helpful hints are available at http://support.microsoft.com/kb/816307.