By default, I/O throttling is turned on for all paths with DMP configured to wait for a maximum of 10 seconds for outstanding I/O requests to succeed. 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 \
See "Displaying recovery option values" on page 170.
The following example displays the I/O throttling setting for the paths to the enclosure
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 \
The following example shows how to disable I/O throttling for the paths to the enclosure
vxdmpadm setattr enclosure enc0 recoveryoption=nothrottle
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 \
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.
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.
queuedepth attributes are mutually exclusive.
The following example sets the value of
iotimeout to 60 seconds for the enclosure
vxdmpadm setattr enclosure enc0 recoveryoption=throttle \
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 \
recoveryoption=default resets I/O throttling to the default settings corresponding to
iotimeout=10, for example:
vxdmpadm setattr arraytype A/A recoveryoption=default
This command also has the effect of configuring a fixed-retry limit of 5 on the paths.
See "Configuring the response to I/O failures" on page 167.
Note The I/O throttling settings are persistent across reboots of the system.