VERITAS Volume Manager 4.1 Administrator's Guide

Performance Monitoring and Tuning
Tuning VxVM
Chapter 12412
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 48 for
more information.
voldrl_max_drtregs
The maximum number of dirty regions that can exist for non-sequential
DRL on a volume. 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 sectors (2MB).
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.
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.