VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

Tuning VxVM
298 VERITAS Volume Manager Administrator’s Guide
A write request to amirrored volume thatis greaterthan 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_default
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.
voliot_iobuf_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 size of this tunable 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_limit
The upper limit to the size of memory that can be used for storing tracing buffers in
the kernel. Tracing buffers are used by the VxVM kernel to store the tracing event
records. As tracebuffers are requested tobe storedin thekernel, the memory for them
is drawn from this pool.
Increasing this size can allow additional tracing to be performed at the expense of
system memory usage. Setting this value to a size greater than can readily be
accommodated on the system is inadvisable.
The default value for this tunable is 131072 bytes (128KB).