Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Administering DMP Using vxdmpadm
124 VERITAS Volume Manager Administrator’s Guide
◆ singleactive
This policy routes I/O down one single active path. This is the default policy for A/P
arrays with one active path per controller, where the other paths are used in case of
failover. If configured for A/A arrays, there is no load balancing across the paths, and
the alternate paths are only used to provide high availability (HA). If the currently
active path fails, I/O is switched to an alternate active path. No further configuration
is possible as the single active path is selected by DMP.
The following example sets the I/O policy to singleactive for JBOD disks:
# vxdmpadm setattr arrayname DISK iopolicy=singleactive
Example of Applying Load Balancing in a SAN
This example describes how to configure load balancing in a SAN environment where
there are multiple primary paths to an Active/Passive device through several SAN
switches. As can be seen in this sample output from the vxdisk list command, the
device c3t2d15 has eight primary paths:
# vxdisk list c3t2d15
Device: c3t2d15
...
numpaths: 8
c2t0d15 state=enabled type=primary
c2t1d15 state=enabled type=primary
c3t1d15 state=enabled type=primary
c3t2d15 state=enabled type=primary
c4t2d15 state=enabled type=primary
c4t3d15 state=enabled type=primary
c5t3d15 state=enabled type=primary
c5t4d15 state=enabled type=primary
In addition, the device is in the enclosure ENC0, belongs to the disk group mydg, and
contains a simple concatenated volume myvol1.
The first step is to enable the gathering of DMP statistics:
# vxdmpadm iostat start
Next the dd command is used to apply an input workload from the volume:
# dd if=/dev/vx/rdsk/mydg/myvol1 of=/dev/null &