In the release notes section 2.1.4.2 for Fedora 10, it says "Systems that use Logical Volume Management (LVM) and the device mapper usually do not require relabeling." This is incorrect if you have a mirrored LVM partition, since the UUID for the mirrored partition is not unique: /dev/mapper/VolGroup00-lvol0_mimage_1: UUID="c9bee71a-ebda-4357-a509-cd92e4a60697" SEC_TYPE="ext2" TYPE="ext3" /dev/mapper/VolGroup00-lvol0_mimage_0: UUID="c9bee71a-ebda-4357-a509-cd92e4a60697" SEC_TYPE="ext2" TYPE="ext3" /dev/mapper/VolGroup00-lvol0: UUID="c9bee71a-ebda-4357-a509-cd92e4a60697" TYPE="ext3" LABEL="mirrored" SEC_TYPE="ext2" If there is no label, with the UUID mount can pick up one of the mirror images (lvol0_mimage_1 or lvol0_migage_0) which will fail. This is probably a bug in blkid or anaconda as well, so I will file one under blkid. For the release notes, it should probably mention that mirrored LVM partitions do need to be labeled.
Regardless of a bug in blkid/anaconda, they still have identical UUIDs, so it is worth specifying to use labels in that case. Fixed and should appear in the next update (web and/or fedora-release-notes update.)