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482 Performance monitoring and tuning
Tuning VxVM
volcvm_smartsync
If set to 0, volcvm_smartsync disables SmartSync on shared disk groups. If
set to 1, this parameter enables the use of SmartSync with shared disk groups.
See“SmartSync recovery accelerator” on page 62 for more information.
voldrl_max_drtregs
The maximum number of dirty regions that can exist on the system for non-
sequential DRL on volumes. A larger value may result in improved system
performance at the expense of recovery time. This tunable can be used to
regulate the worse-case recovery time for the system following a failure.
The default value for this tunable is 2048.
voldrl_max_seq_dirty
The maximum number of dirty regions allowed for sequential DRL. This is
useful for volumes that are usually written to sequentially, such as database
logs. Limiting the number of dirty regions allows for faster recovery if a crash
occurs.
The default value for this tunable is 3.
voldrl_min_regionsz
The minimum number of sectors for a dirty region logging (DRL) volume region.
With DRL, VxVM logically divides a volume into a set of consecutive regions.
Larger region sizes tend to cause the cache hit-ratio for regions to improve. This
improves the write performance, but it also prolongs the recovery time.
The VxVM kernel currently sets the default value for this tunable to 512 sectors.
Note: If DRL sequential logging is configured, the value of
voldrl_min_regionsz must be set to at least half the value of vol_maxio.
voliomem_chunk_size
The granularity of memory chunks used by VxVM when allocating or releasing
system memory. A larger granularity reduces CPU overhead due to memory
allocation by allowing VxVM to retain hold of a larger amount of memory.
The default size for this tunable is 64KB.