VERITAS Volume Manager 3.1 Administrator's Guide

Volume Tasks
Resizing a Volume
Chapter 6 245
NOTE The vxvol set len command cannot increase the size of a volume unless
the needed space is available in the plexes of the volume. When the size
of a volume is reduced using the vxvol set len command, the freed
space is not released into the free space pool.
Changing the Volume Read Policy
Volume Manager offers the choice of the following read policies:
• round—reads each plex in turn in “round-robin” fashion for each
nonsequential I/O detected. Sequential access causes only one plex to
be accessed. This takes advantage of the drive or controller
read-ahead caching policies.
• prefer—reads first from a plex that has been named as the
preferred plex.
• select—chooses a default policy based on plex associations to the
volume. If the volume has an enabled striped plex, the select option
defaults to preferring that plex; otherwise, it defaults to round-robin.
The read policy can be changed from round to prefer (or the reverse),
or to a different preferred plex. The vxvol rdpol command sets the
read policy for a volume.
To set the read policy to round, use the following command:
# vxvol rdpol round volume_name
For example, to set the read policy for volume vol01 to a round-robin
read, use the following command:
# vxvol rdpol round vol01
To set the read policy to prefer, use the following command:
# vxvol rdpol prefer volume_name preferred_plex_name
For example, to set the policy for vol01 to read preferentially from
the plex vol01-02, use the following command:
# vxvol rdpol prefer vol01 vol01-02
To set the read policy to select, use the following command:
# vxvol rdpol select volume_name