Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

This policy sends I/O on paths that have the minimum
number of outstanding I/O requests in the queue for a LUN.
No further configuration is possible as DMP automatically
determines the path with the shortest queue.
The following example sets the I/O policy to minimumq for
a JBOD:
# vxdmpadm setattr enclosure Disk \
iopolicy=minimumq
This is the default I/O policy for all arrays.
minimumq
This policy is useful when the paths in a SAN have unequal
performance, and you want to enforce load balancing
manually. You can assign priorities to each path based on
your knowledge of the configuration and performance
characteristics of the available paths, and of other aspects
of your system.
See “Setting the attributes of the paths to an enclosure”
on page 177.
In this example, the I/O policy is set to priority for all
SENA arrays:
# vxdmpadm setattr arrayname SENA \
iopolicy=priority
priority
This policy shares I/O equally between the paths in a
round-robin sequence. For example, if there are three paths,
the first I/O request would use one path, the second would
use a different path, the third would be sent down the
remaining path, the fourth would go down the first path,
and so on. No further configuration is possible as this policy
is automatically managed by DMP.
The next example sets the I/O policy to round-robin for
all Active/Active arrays:
# vxdmpadm setattr arraytype A/A \
iopolicy=round-robin
round-robin
183Administering Dynamic Multi-Pathing
Administering DMP using vxdmpadm