Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Tuning VxVM
416 VERITAS Volume Manager Administrator’s Guide
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.
voliomem_maxpool_sz
The maximum memory requested from the system by VxVM for internal purposes. This
tunable has a direct impact on the performance of VxVM as it prevents one I/O operation
from using all the memory in the system.
VxVM allocates two pools that can grow up to voliomem_maxpool_sz, one for RAID-5
and one for mirrored volumes.
A write request to a RAID-5 volume that is greater than voliomem_maxpool_sz/10 is
broken up and performed in chunks of size voliomem_maxpool_sz/10.
A write request to a mirrored volume that is greater than voliomem_maxpool_sz/2 is
broken up and performed in chunks of size voliomem_maxpool_sz/2.
The default value for this tunable is 4M.
Note The value of voliomem_maxpool_sz must be at least 10 times greater than the
value of vol_maxio.
voliot_errbuf_dflt
The default size of the buffer maintained for error tracing events. This buffer is allocated
at driver load time and is not adjustable for size while VxVM is running.
The default size for this buffer is 16384 bytes (16KB).
Increasing this buffer can provide storage for more error events at the expense of system
memory. Decreasing the size of the buffer can result in an error not being detected via the
tracing device. Applications that depend on error tracing to perform some responsive
action are dependent on this buffer.