Veritas Volume Manager supports the use of the following types of logs and maps with volumes:

• FastResync Maps are used to perform quick and efficient resynchronization of mirrors.

  These maps are supported either in memory (Non-Persistent FastResync), or on disk as part of a DCO volume (Persistent FastResync). Two types of DCO volume are supported:

  • Version 0 DCO volumes only support Persistent FastResync for the traditional third-mirror break-off type of volume snapshot.

  • Version 20 DCO volumes, introduced in VxVM 4.0, support DRL logging (see below) and Persistent FastResync for full-sized and space-optimized instant volume snapshots.

• Dirty region logs allow the fast recovery of mirrored volumes after a system crash.

  These logs are supported either as DRL log plexes, or as part of a version 20 DCO volume. Refer to the following sections for information on creating a volume on which DRL is enabled:

• RAID-5 logs are used to prevent corruption of data during recovery of RAID-5 volumes.

  These logs are configured as plexes on disks other than those that are used for the columns of the RAID-5 volume.