Mirroring Using Minimal Physical Disk Space

The master device and a mirror of the user database transaction log are stored in separate partitions on one physical disk. The other disk stores the user database and its transaction log in two separate disk partitions.

If the disk with the user database fails, you can restore the user database on a new disk from your backups and the mirrored transaction log.

If the disk with the master device fails, you can restore the master device from a database dump of the master database and remirror the user database’s transaction log.

This figure illustrates the “minimum guaranteed configuration” for database recovery in case of hardware failure.

Graphic showing two disk devices, with the second containing a mirror of the transaction log of the first disk.

This configuration minimizes the amount of disk storage required, but the mirror of the transaction log ensures full recovery. However, this configuration does not provide nonstop recovery because the master and user databases are not being mirrored and must be recovered from backups.