VERITAS Volume Manager 4.1 Administrator's Guide

Administering Dynamic Multipathing (DMP)
Administering DMP Using vxdmpadm
Chapter 3144
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 &
By running the vxdmpadm iostat command to display the DMP statistics for the device, it can
be seen that all I/O is being directed to one subpath, c5t4d15:
# vxdmpadm iostat show dmpnodename=c3t2d15 interval=5 count=2
...
cpu usage = 11294us per cpu memory = 32768b
OPERATIONS KBYTES AVG TIME(ms)
PATHNAME READS WRITES READS WRITES READS WRITES
c2t0d15 0 0 0 0 0.000000 0.000000
c2t1d15 0 0 0 0 0.000000 0.000000
c3t1d15 0 0 0 0 0.000000 0.000000
c3t2d15 0 0 0 0 0.000000 0.000000
c4t2d15 0 0 0 0 0.000000 0.000000
c4t3d15 0 0 0 0 0.000000 0.000000
c5t3d15 0 0 0 0 0.000000 0.000000
c5t4d15 5493 0 5493 0 0.411069 0.000000
The vxdmpadm command is used to display the I/O policy for the enclosure that contains the
device:
# vxdmpadm getattr enclosure ENC0 iopolicy