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

Configuring the I/O throttling mechanism
By default, DMP is configured with I/O throttling turned off for all paths. To
display the current settings for I/O throttling that are applied to the paths to an
enclosure, array name or array type, use the vxdmpadm getattr command.
See “Displaying recovery option values” on page 192.
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]
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.
The following example sets the value of iotimeout to 60 seconds for the enclosure
enc0:
# vxdmpadm setattr enclosure enc0 recoveryoption=throttle \
iotimeout=60
Specify recoveryoption=default to reset I/O throttling to the default settings,
as follows:
# vxdmpadm setattr arraytype A/A recoveryoption=default
191Administering Dynamic Multi-Pathing
Administering DMP using vxdmpadm