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478 Performance monitoring and tuning
Tuning VxVM
dmp_restore_policy
The DMP restore policy, which can be set to 0 (CHECK_ALL), 1
(CHECK_DISABLED), 2 (CHECK_PERIODIC), or 3 (CHECK_ALTERNATE).
The value of this tunable is only changeable by using the vxdmpadm start
restore
command.
dmp_retry_count
If an inquiry succeeds on a path, but there is an I/O error, the number of retries
to attempt on the path. The default number of retries is 30.
The value of this tunable is changed by an entry in the /kernel/drv/
vxdmp.conf file, or by using the
vxdmpadm settune command.
See “Configuring the response to I/O failures” on page 156.
dmp_retry_timeout
The maximum time period for which DMP retries the SCSI-3 Persistent Reserve
operation with A/P arrays.
The default value is 0 seconds, which disables this feature.
This parameter has no direct effect on I/O processing by DMP.
Disabling a switch port can trigger a fabric reconfiguration, which can take time
to stabilize. During this period, attempting to register PGR keys through the
secondary path to an array may fail with an error condition, such as unit
attention or device reset, or the return of vendor-specific sense data.
The retry period allows a fabric reconfiguration (usually a transient condition)
to not be seen as an error by DMP.
Do not set the value of the retry period too high. This can delay the failover
process, and result in I/O sluggishness or suppression of I/O activity during the
retry period.
The value of this tunable is changed by using the
vxdmpadm settune command.
dmp_scsi_timeout
Determines the timeout value to be set for any SCSI command that is sent via
DMP. If the HBA does not receive a response for a SCSI command that it has sent
to the device within the timeout period, the SCSI command is returned with a
failure error code.
The default value is 60 seconds.
The value of this tunable is changed by using the
vxdmpadm settune command.