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

Chapter 12, Performance Monitoring and Tuning
Tuning VxVM
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voliot_iobuf_max
The maximum buffer size that can be used for a single trace buffer. Requests of a
buffer larger than this size are silently truncated to this size. A request for a maximal
buffer size from the tracing interface results (subject to limits of usage) in a buffer of
this size.
The default size for this buffer is 65536 bytes (64KB).
Increasing this buffer can provide for larger traces to be taken without loss for very
heavily used volumes.Careshould betaken notto increase this valueabove thevalue
for the voliot_iobuf_limit tunable value.
voliot_max_open
The maximum number of tracing channels that can be open simultaneously. Tracing
channels are clone entry points into the tracing device driver. Each vxtrace process
running on a system consumes a single trace channel.
The default number of channels is 32. The allocation of each channel takes up
approximately 20 bytes even when not in use.
volraid_minpool_sz
The initialamount of memory that is requested from thesystem by VxVM for RAID-5
operations. The maximum size of this memory pool is limited by the value of
voliomem_maxpool_sz.
The default value for this tunable is 2048 sectors (2MB).
volraid_rsrtransmax
The maximum number of transient reconstruct operations that can be performed in
parallel for RAID-5. A transient reconstruct operation is one that occurs on a
non-degraded RAID-5 volume that has not been predicted. Limiting the number of
these operations thatcan occur simultaneously removes the possibilityof flooding the
system with many reconstruct operations, and so reduces the risk of causing memory
starvation.
The default number of transient reconstruct operations that can be performed in
parallel is 1.
Increasingthissize improvestheinitial performanceon thesystemwhen a failurefirst
occurs and before a detach of a failing object is performed, but can lead to memory
starvation.