VERITAS Volume Manager 4.1 Administrator's Guide

Creating Volumes
Types of Volume Layouts
Chapter 7226
Types of Volume Layouts
VxVM allows you to create volumes with the following layout types:
• Concatenated—A volume whose subdisks are arranged both
sequentially and contiguously within a plex. Concatenation allows a
volume to be created from multiple regions of one or more disks if
there is not enough space for an entire volume on a single region of a
disk. For more information, see “Concatenation and Spanning” on
page 19.
• Striped—A volume with data spread evenly across multiple disks.
Stripes are equal-sized fragments that are allocated alternately and
evenly to the subdisks of a single plex. There must be at least two
subdisks in a striped plex, each of which must exist on a different
disk. Throughput increases with the number of disks across which a
plex is striped. Striping helps to balance I/O load in cases where high
traffic areas exist on certain subdisks. For more information, see
“Striping (RAID-0)” on page 22.
• Mirrored—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. For
more information, see “Mirroring (RAID-1)” on page 25.
• RAID-5—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 accessed. However, in comparison to mirroring, the use
of parity to implement data redundancy reduces the amount of space
required. For more information, see “RAID-5 (Striping with Parity)”
on page 30.
• Mirrored-stripe—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