Unmirroring - DiskSuite Tool does not support unmirroring root (/), /opt, /usr, or swap, or any other file system that cannot be unmounted while the system is running. Instead, use the command line procedure for these file systems.
Attaching - You can attach a submirror to a mirror without interrupting service. You attach submirrors to mirrors to create two- and three-way mirrors.
Detach vs. Offline - When you place a submirror offline, you prevent the mirror from reading from and writing to the submirror, but you preserve the submirror's logical association to the mirror. While the submirror is offline, DiskSuite keeps track of all writes to the mirror and they are written to the submirror when it is brought back online. By performing an optimized resync, DiskSuite only has to resync data that has changed, not the entire submirror. When you detach a submirror, you sever its logical association to the mirror. Typically you place a submirror offline to perform maintenance; you detach a submirror to remove it.