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

A volume with multiple data plexes that duplicate the information
contained in a volume. Although a volume can have a single data
plex, at least two are required for true mirroring to provide
redundancy of data. For the redundancy to be useful, each of these
data plexes should contain disk space from different disks.
See “Mirroring (RAID-1)” on page 41.
Mirrored
A volume that uses striping to spread data and parity evenly across
multiple disks in an array. Each stripe contains a parity stripe
unit and data stripe units. Parity can be used to reconstruct data
if one of the disks fails. In comparison to the performance of
striped volumes, write throughput of RAID-5 volumes decreases
since parity information needs to be updated each time data is
modified. However, in comparison to mirroring, the use of parity
to implement data redundancy reduces the amount of space
required.
See “RAID-5 (striping with parity)” on page 44.
RAID-5
A volume that is configured as a striped plex and another plex
that mirrors the striped one. This requires at least two disks for
striping and one or more other disks for mirroring (depending on
whether the plex is simple or striped). The advantages of this
layout are increased performance by spreading data across
multiple disks and redundancy of data.
See “Striping plus mirroring (mirrored-stripe or RAID-0+1)”
on page 42.
Mirrored-stripe
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” on page 49.
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)” on page 43.
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
297Creating volumes
Types of volume layouts