Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

464 Performance monitoring and tuning
Tuning VxVM
command. A value can also be set for paths to individual arrays by using the vxdmpadm
command as described in “Configuring the I/O throttling mechanism” on page 151.
dmp_restore_daemon_cycles
If the DMP restore policy is CHECK_PERIODIC, the number of cycles after which the
CHECK_ALL policy is called. The value of this tunable can also be changed by using the
vxdmpadm command as described in “Configuring DMP path restoration policies” on
page 153.
dmp_restore_daemon_interval
The time in seconds between two invocations of the DMP path restoration thread. The
value of this tunable can also be changed by using the
vxdmpadm command as described
in “Configuring DMP path restoration policies” on page 153.
dmp_restore_daemon_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 can also be changed by using the
vxdmpadm command as described
in “Configuring DMP path restoration policies” on page 153.
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 5. The value of this tunable may be changed
by using the
vxdmpadm settune command. The value of this tunable can also be set for
the paths to individual arrays by using the
vxdmpadm command as described in
“Configuring the response to I/O failures” on page 149.
vol_checkpt_default
The interval at which utilities performing recoveries or resynchronization operations load
the current offset into the kernel as a checkpoint. A system failure during such operations
does not require a full recovery, but can continue from the last reached checkpoint.
The default value of the checkpoint is 10240 sectors (10MB).
Increasing this size reduces the overhead of checkpointing on recovery operations at the
expense of additional recovery following a system failure during a recovery.
vol_default_iodelay
The count in clock ticks for which utilities pause if they have been directed to reduce the
frequency of issuing I/O requests, but have not been given a specific delay time. This