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Adding logs and maps to volumes

In Veritas Volume Manager, several types of volume logs and maps are supported:

• FastResync Maps are used to perform quick and efficient resynchronization of mirrors (see FastResync for details). 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 volumes are supported:
  • Version 0 DCO volumes only support Persistent FastResync for the traditional third-mirror break-off type of volume snapshot. See Version 0 DCO volume layout, and Adding a version 0 DCO and DCO volume for more information.
  • 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. See Version 20 DCO volume layout, and Preparing a volume for DRL and instant snapshots for more information.

    See Enabling FastResync on a volume for information on how to enable Persistent or Non-Persistent FastResync on a volume.

• Dirty Region Logs allow the fast recovery of mirrored volumes after a system crash (see Dirty region logging for details). 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 enabling DRL on a volume:
  • Adding traditional DRL logging to a mirrored volume describes how to add DRL log plexes to a volume.
  • Preparing a volume for DRL and instant snapshots describes how to configure DRL for a volume using a version 20 DCO volume.
• RAID-5 logs are used to prevent corruption of data during recovery of RAID-5 volumes (see RAID-5 logging for details). These logs are configured as plexes on disks other than those that are used for the columns of the RAID-5 volume.

  See Adding a RAID-5 log for information on adding RAID-5 logs to a RAID-5 volume.