Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

A volume constructed from other volumes. Non-layered volumes
are constructed by mapping their subdisks to VM disks. Layered
volumes are constructed by mapping their subdisks to underlying
volumes (known as storage volumes), and allow the creation of
more complex forms of logical layout. Examples of layered volumes
are striped-mirror and concatenated-mirror volumes.
See Layered volumes.
A striped-mirror volume is created by configuring several mirrored
volumes as the columns of a striped volume. This layout offers
the same benefits as a non-layered mirrored-stripe volume. In
addition it provides faster recovery as the failure of single disk
does not force an entire striped plex offline.
See Mirroring plus striping (striped-mirror, RAID-1+0 or RAID-10).
A concatenated-mirror volume is created by concatenating several
mirrored volumes. This provides faster recovery as the failure of
a single disk does not force the entire mirror offline.
Layered Volume
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 65.
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 68.
See “Creating a volume with a version 0 DCO volume” on page 290.
■ 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 68.
See “Creating a volume with a version 20 DCO volume” on page 293.
See “Enabling FastResync on a volume” on page 338.
■ Dirty region logs allow the fast recovery of mirrored volumes after a system
crash.
Creating volumes
Types of volume layouts
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