ASR Cannot Restore System Disk to Replacement Disk of Identical Size

When you attempt to use Automated System Recovery (ASR) to restore to a replacement system or disk, you may receive the following error message, even if the new system disk appears to be the same size as the original system disk:

This behavior can occur if the replacement disk is slightly smaller than the original system disk, even though they are shown as having the same amount of space. This can occur because two disks that appear to be of the same size may not have the same number of sectors, due to differences in disk geometry and rounding errors in the display of disk space.

To resolve this behavior, use a replacement disk that has identical disk geometry to the original disk, or use a larger disk.

This behavior is by design.

Slight differences in the number of available sectors on a disk may also occur between disks that are the same make and model, but which have different firmware revisions.