Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

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■ Underscores (_)
■ Periods (.)
A tag name must start with either a letter or an underscore.
Tag values can consist of any ASCII character that has a decimal value from 32
through 127. If a tag value includes spaces, quote the specification to protect it
from the shell, as follows:
# vxassist -g mydg settag myvol "dbvol=table space 1"
The list operation understands dotted tag hierarchies. For example, the listing
for tag=a.b includes all volumes that have tag names starting with a.b.
The tag names site, udid, and vdid are reserved. Do not use them. To avoid
possible clashes with future product features, do not start tag names with any of
the following strings: asl, be, nbu, sf, symc, or vx.
Changing the read policy for mirrored volumes
VxVM offers the choice of the following read policies on the data plexes in a
mirrored volume:
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 approach takes advantage of
the drive or controller read-ahead caching policies.
round
Reads first from a plex that has been named as the preferred
plex.
prefer
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.
select
Reads preferentially from plexes at the locally defined site.
This method is the default policy for volumes in disk groups
where site consistency has been enabled.
For disk group versions 150 or higher and if the local site
has a SSD based plex, it will be preferred.
See “Configuring site consistency on a disk group”
on page 494.
siteread
335Administering volumes
Changing the read policy for mirrored volumes