VERITAS Volume Manager 3.1 Storage Administrator Administrator's Guide

Volume Tasks
Creating a Volume
Chapter 4 151
each volume layout.
Table 4-1 Layout Comparison
Layout Advantages Disadvantages
Concatenated • The volume can consist of disk
regions that are not adjacent.
• The volume can span multiple
disks. A spanned volume can
have a greater capacity than a
single disk.
• The volume can be mirrored to
protect data against disk
failure and reduce the risk of
data loss.
• There is a risk of data loss if the
volume is not mirrored.
• Spanning a volume across
multiple disks increases the
chance that a disk failure will
result in the failure of the volume.
• Concatenation does not improve
I/O performance.
Striped • Striping provides improved
read and write performance.
• Striping can help to balance
the I/O load from multi-user
applications across multiple
disks.
• The volume can be mirrored to
protect data against disk
failure.
• There is a risk of data loss if the
volume is not mirrored.
• Striping a volume across multiple
disks increases the chance that a
disk failure will result in the
failure of the volume.
• A striped volumerequires at least
two disks.
RAID-5 • RAID-5 provides protection
against disk failure and
reduces the risk of data loss.
• RAID-5 provides data
redundancy by storing parity
(a calculated value) on the
disks. If a disk fails, the parity
is used to reconstruct the
missing data.
• RAID-5 requires less storage
space than mirroring.
• RAID-5 provides improved
read performance.
• RAID-5 provides relatively slow
write performance.
• RAID-5 volumes cannot be
mirrored.
• A RAID-5 volume requires at
least three disks. If logging is
enabled, a RAID-5 volume
requires at least four disks.
• A RAID-5 volume cannot survive
multiple disk failures. However,
optional RAID-5 logs reduce this
risk.
• If one of the volume’s disks is
inaccessible, performance is
degraded.