Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

Supported volume logs and maps
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.
See “FastResync” on page 63.
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.
See “Version 0 DCO volume layout” on page 66.
See “Creating a volume with a version 0 DCO volume” on page 313.
■ 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” on page 66.
See “Creating a volume with a version 20 DCO volume” on page 316.
See “Enabling FastResync on a volume” on page 373.
■ Dirty region logs allow the fast recovery of mirrored volumes after a system
crash.
See “Dirty region logging” on page 57.
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:
See “Creating a volume with dirty region logging enabled” on page 316.
See “Creating a volume with a version 20 DCO volume” on page 316.
■ RAID-5 logs are used to prevent corruption of data during recovery of RAID-5
volumes.
See “RAID-5 logging” on page 49.
These logs are configured as plexes on disks other than those that are used
for the columns of the RAID-5 volume.
See “Creating a RAID-5 volume” on page 321.
Creating volumes
Types of volume layouts
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