Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

Table 15-1
Kernel tunable parameters for VxVM (continued)
DescriptionParameter
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 this size,
one for RAID-5 and one for mirrored volumes.
Additional pools are allocated if instant (Copy On
Write) snapshots are present.
A write request to a RAID-5 volume that is greater than
one fourth of the pool size is broken up and performed
in chunks of one tenth of the pool size.
A write request to a mirrored volume that is greater
than the pool size is broken up and performed in
chunks of the pool size.
The default value is 134217728 (128MB)
The value of voliomem_maxpool_sz must be at least
10 times greater than the value of vol_maxio.
voliomem_maxpool_sz
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 value 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.
voliot_errbuf_dflt
The default size for the creation of a tracing buffer in
the absence of any other specification of desired kernel
buffer size as part of the trace ioctl.
The default value is 8192 bytes (8KB).
If trace data is often being lost due to this buffer size
being too small, then this value can be tuned to a more
generous amount.
voliot_iobuf_default
501Performance monitoring and tuning
Tuning VxVM