Installation Guide

When all paths to a disk fail, there may be certain paths that have a temporary failure and are
likely to be restored soon. If I/Os are not retried for a period of time, the I/Os may be failed to
the application layer even though some paths are experiencing a transient failure. For more robust
handling of such transient errors, the dmp_lun_retry_timeout tunable provides a time-based
retry mechanism at the LUN level. If the tunable is set to a non-zero value, I/Os to a disk with all
failed paths will be retried until the dmp_lun_retry_timeout interval expires or until the I/O
succeeds on one of the paths, whichever happens first.
Use the following command to set and retrieve the tunable:
vxdmpadm gettune dmp_lun_retry_timeout
vxdmpadm settune dmp_lun_retry_timeout=<interval>
Where the value for <interval> is in seconds.
The default value of this tunable is 0, which means that the paths are probed only once. HP
recommends a value of 120 seconds.
You need to set the pftostate and dmp_lun_retry_timeout tunables only once as the values
you set are persistent across reboots.
If these tunables are not set as recommended, certain transient I/O error conditions could result
in interruptions to volume availability.
I/O Robustness Recommendations 63