HP Veritas Volume Manager 5.0 -UX 11i v3 manual

158Administering dynamic multipathing (DMP)

Administering DMP using vxdmpadm

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-namearraynamenamearraytype type}\ recoveryoption=throttle {iotimeout=secondsqueuedepth=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 40. 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

Specifying recoveryoption=default resets I/O throttling to the default settings corresponding to recoveryoption=throttle iotimeout=10, for example:

#vxdmpadm setattr arraytype A/A recoveryoption=default

This command also has the effect of configuring a fixed-retry limit of 30 on the paths.

See “Configuring the response to I/O failures” on page 156 for details.

Note: The I/O throttling settings are persistent across reboots of the system.