To help optimize performance for different types of volumes, VxVM supports the following read policies on data plexes:
round—
a round-robin read policy, where all plexes in the volume take turns satisfying read requests to the volume.
prefer
—a preferred-plex read policy, where the plex with the highest performance usually satisfies read requests. If that plex fails, another plex is accessed.
select—
default read policy, where the appropriate read policy for the configuration is selected automatically. For example, prefer
is selected when there is only one striped plex associated with the volume, and round
is selected in most other cases.
Note You cannot set the read policy on a RAID-5 data plex. RAID-5 plexes have their own read policy (RAID).
For instructions on how to configure the read policy for a volume's data plexes, see Changing the read policy for mirrored volumes.
In the configuration example shown in Use of mirroring and striping for improved performance, the read policy of the mirrored-stripe volume labeled Hot
Vol
is set to prefer
for the striped plex PL1
. This policy distributes the load when reading across the otherwise lightly-used disks in PL1
, as opposed to the single disk in plex PL2
. (HotVol
is an example of a mirrored-stripe volume in which one data plex is striped and the other data plex is concatenated.)
Use of mirroring and striping for improved performance
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Note To improve performance for read-intensive workloads, you can attach up to 32 data plexes to the same volume. However, this would usually be an ineffective use of disk space for the gain in read performance.