If a system that you need to upgrade has overlapping slices on any of the attached disks (excluding the backup slice), the upgrade configuration process fails. If you are using Disk Space Reallocation, the auto-layout process fails.
Workaround: Change or delete the overlapping slices by using the format command.
Note that changes to slices will cause data loss on both the slice being changed and on any slices that is being overlapped by the changed slice. Any data on the affected slices should be backed up before slice manipulation is attempted.