Mirroring, described Mirroring, is the mechanism by which a single database server maintains a copy of a specific dbspace on a separate disk. This mechanism protects the data in mirrored dbspaces against disk failure because the database server automatically updates data on both disks and automatically uses the other disk if one of the dbspaces fails. Alternatively, a cluster duplicates on an entirely separate database server all the data that a database server manages, not just the specified dbspaces. Because clustering involves two separate database servers, it protects the data that these database servers manage, not just against disk failures, but against all types of database server failures, including a computer failure or the catastrophic failure of an entire site.