VERITAS Volume Manager 3.1 Administrator's Guide

Performance Monitoring
Performance Monitoring
Chapter 9396
Performance Monitoring
There are two sets of priorities for a system administrator. One set is
physical, concerned with the hardware. The other set is logical,
concerned with managing the software and its operations.
Performance Priorities
The physical performance characteristics address the balance of the I/O
on each drive and the concentration of the I/O within a drive to minimize
seek time. Based on monitored results, you can move subdisk locations to
balance the disks.
The logical priorities involve software operations and how they are
managed. Based on monitoring, certain volumes can be mirrored or
striped to improve their performance. Overall throughput can be
sacrificed to improve the performance of critical volumes. Only the
system administrator can decide what is important on a system and
what tradeoffs to make.
Best performance can generally be achieved by striping and mirroring all
volumes across a reasonable number of disks and mirroring between
controllers when possible. This tends to even out the load between all
disks.However, this usuallymakes theVolume Manager more difficult to
administer. If you have a large number of disks (hundreds or thousands),
you can place disks in groups of 10 (using disk groups), where each group
is used to stripe and mirror s set of volumes. This still provides good
performance and eases the task of administration.
Getting Performance Data
Volume Manager provides two types of performance information: I/O
statistics and I/O traces. Each type can help in performance monitoring.
I/O statistics are retrieved using the vxstat command, and I/O tracing
can be retrieved using the vxtrace utility. A brief discussion of each of
these utilities is included in this chapter.
Obtaining I/O Statistics (vxstat Command)
The vxstat command accesses activity information on volumes, plexes,
subdisks, and disks under Volume Manager control. The vxstat utility