vxdmpadm getattr
156Administering dynamic multipathing (DMP)

Administering DMP using vxdmpadm

Configuring the response to I/O failures

By default, DMP is configured to retry a failed I/O request up to 5 times for a single path. To display the current settings for handling I/O request failures that are applied to the paths to an enclosure, array name or array type, use the

command:

#vxdmpadm getattr \{enclosure enc-namearrayname namearraytype type} \ recoveryoptionSee “Displaying recoveryoption values” on page 159 for more information.

The following example displays the I/O request failure setting for the paths to the enclosure enc0:

#vxdmpadm getattr enclosure enc0 recoveryoption

The vxdmpadm setattr command can be used to configure how DMP responds to failed I/O requests on the paths to a specified enclosure, disk array name, or type of array.

The following form of the command sets a limit for the number of times that DMP will attempt to retry sending an I/O request on a path:

#vxdmpadm setattr \

{enclosure enc-namearraynamenamearraytype type} \ recoveryoption=fixedretry retrycount==n

The value of the argument to retrycount specifies the number of retries to be attempted before DMP reschedules the I/O request on another available path, or fails the request altogether.

As an alternative to specifying a fixed number of retries, the following version of the command specifies how long DMP should allow an I/O request to be retried on a path:

#vxdmpadm setattr \

{enclosure enc-namearraynamenamearraytype type} \ recoveryoption=timebound iotimeout==seconds

The value of the argument to iotimeout specifies the time in seconds that DMP waits for an outstanding I/O request to succeed before it reschedules the request on another available path, or fails the I/O request altogether. The effective number of retries is the value of iotimeout divided by the sum of the times taken for each retry attempt. DMP abandons retrying to send the I/O request before the specified time limit has expired if it predicts that the next retry will take the total elapsed time over this limit.

The default value of iotimeout is 10 seconds. For some applications, such as Oracle, it may be desirable to set iotimeout to a larger value, such as 60 seconds.

Note: The fixedretry and timebound settings are mutually exclusive.