Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

150 Administering dynamic multipathing (DMP)
Administering DMP using vxdmpadm
# vxdmpadm getattr \
{enclosure enc-name|arrayname name|arraytype type}\
recoveryoption
See “Displaying recoveryoption values” on page 151 for more information.
The following example displays the I/O throttling setting for the paths to the enclosure
enc0:
# vxdmpadm getattr enclosure enc0 recoveryoption
If enabled, I/O throttling imposes a small overhead on CPU and memory usage because of
the activity of the statistics-gathering daemon. If I/O throttling is disabled, the daemon no
longer collects statistics, and remains inactive until I/O throttling is re-enabled.
To turn off I/O throttling, use the following form of the
vxdmpadm setattr command:
# vxdmpadm setattr \
{enclosure enc-name|arrayname name|arraytype type}\
recoveryoption=nothrottle
The following example shows how to disable I/O throttling for the paths to the enclosure
enc0:
# vxdmpadm setattr enclosure enc0 recoveryoption=nothrottle
The vxdmpadm setattr command can be used to enable I/O throttling on the paths to a
specified enclosure, disk array name, or type of array:
# vxdmpadm setattr \
{enclosure enc-name|arrayname name|arraytype type}\
recoveryoption=throttle {iotimeout=seconds|queuedepth=n}
If the iotimeout attribute is specified, its argument specifies the time in seconds that
DMP waits for an outstanding I/O request to succeed before invoking I/O throttling on the
path. The default value of iotimeout is 10 seconds. Setting
iotimeout to a larger
value potentially causes more I/O requests to become queued up in the SCSI driver before
I/O throttling is invoked.
If the
queuedepth attribute is specified, its argument specifies the number of I/O requests
that can be outstanding on a path before DMP invokes I/O throttling. The default value of
queuedepth is 20. Setting queuedepth to a larger value allows more I/O requests to
become queued up in the SCSI driver before I/O throttling is invoked.
Note: The iotimeout and queuedepth attributes are mutually exclusive.
The following example sets the value of
iotimeout to 60 seconds for the enclosure
enc0:
# vxdmpadm setattr enclosure enc0 recoveryoption=throttle \
iotimeout=60
The next example sets the value of queuedepth to 30 for the paths to all Active/Active
arrays:
# vxdmpadm setattr arraytype A/A recoveryoption=throttle \
queuedepth=30