HP Serviceguard Storage Management Suite for VERITAS manual Robustness Recommendations

Models: Serviceguard Storage Management Suite for VERITAS

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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

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HP Serviceguard Storage Management Suite for VERITAS manual Robustness Recommendations