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476 Performance monitoring and tuning
Tuning VxVM
The value of this tunable is changed by using the vxdmpadm settune command.
dmp_health_time
DMP detects intermittently failing paths, and prevents I/O requests from being
sent on them. The value of dmp_health_time represents the time in seconds
for which a path must stay healthy. If a path’s state changes back from enabled
to disabled within this time period, DMP marks the path as intermittently
failing, and does not re-enable the path for I/O until dmp_path_age seconds
elapse. The default value of dmp_health_time is 60 seconds. A value of 0
prevents DMP from detecting intermittently failing paths.
The value of this tunable is changed by using the
vxdmpadm settune command.
dmp_log_level
The level of detail that is displayed for DMP console messages. The following
level values are defined:
1 Display all DMP log messages that existed in releases before 5.0. This is
the default setting.
2 Display level 1 messages plus messages that relate to I/O throttling,
suspected paths, repeated path failures and DMP node migration.
3 Display level 1 and 2 messages plus messages that relate to I/O errors,
I/O error analysis and path media errors.
4 Display level 1, 2 and 3 messages plus messages that relate to setting or
changing attributes on a path.
The value of this tunable is changed by using the vxdmpadm settune command.
dmp_path_age
The time for which an intermittently failing path needs to be monitored as
healthy before DMP once again attempts to schedule I/O requests on it. The
default value is 300 seconds. A value of 0 prevents DMP from detecting
intermittently failing paths.
The value of this tunable is changed by using the
vxdmpadm settune command.
dmp_pathswitch_blks_shift
The default number of contiguous I/O blocks (expressed as the integer exponent
of a power of 2; for example 10 represents 1024 blocks) that are sent along a
DMP path to an Active/Active array before switching to the next available path.
The default value of this parameter is set to 10 so that 1024 blocks (1MB) of
contiguous I/O are sent over a DMP path before switching. For intelligent disk
arrays with internal data caches, better throughput may be obtained by