VERITAS Volume Manager 3.5 User's Guide - VERITAS Enterprise Administrator (June 2002)

Chapter 4, Volume Tasks 79
VxVM Volumes
◆ Mirrored Volume
Volumes with concatenated or striped layouts can be mirrored to increase data
availability. All of the data in a mirrored volume is duplicated on at least one other
physical disk. If one of the disks fails, the data can still be accessed from one of the
remaining disks.
The plexes in a mirrored volume typically have the same layout, but a volume can
consist of plexes with different layouts. A mirrored volume has a “mixed” layout if
the plexes in the volume have different layouts.
◆ Layered Volume
A layered volume is built on one or more other volumes. The underlying volumes are
typically mirrored. In layered volumes, mirroring is done at a lower level and with
smaller granularity than with non-layered volumes,so each mirror covers a relatively
small storage region.
Layered volumes tolerate disk failure better than non-layered volumes and provide
improved data redundancy. If a disk in a layered volume fails, only a portion of the
redundancy is lost and recovery time is usually quicker than it would be for a
non-layered volume. Layered volumes also reduce the chance that two disk failures
will result in lost data.
The underlying volumes in a layered volume are used exclusively by VxVM and are
not intended for user manipulation.
With VxVM, you can create the following types of layered volumes:
- Concatenated Pro Volume
A concatenated pro volume is a layered volume that concatenates several
underlying mirror volumes.
- Striped Pro Volume
A striped pro volume is a layered volume that stripes several underlying mirror
volumes.