Although database mirroring can help minimize the risk of data loss, it is still recommended that you back up and validate databases that are participating in a database mirroring system.
You can use the BACKUP DATABASE statement to perform a back up relative to the database server. The BACKUP DATABASE statement is executed on the primary database server, so the file name that is provided should specify a network drive or UNC name that is consistent for both the primary and mirror database servers. See BACKUP statement.
Alternatively, you can perform client-side backups using the dbbackup utility. See Backup utility (dbbackup).