VERITAS Volume Manager 3.1 Administrator's Guide

Performance Monitoring

Chapter 9398

vol testvol 0 0 0 0 0.0 0.0

Additional volume statistics are available for RAID-5 conﬁgurations. See

the vxstat(1M) manual page for more information.

Tracing I/O (vxtrace Command)

The vxtrace command traces operations on volumes. The vxtrace

command either prints kernel I/O errors or I/O trace records to the

standard output or writes the records to a ﬁle in binary format. Tracing

can be applied to speciﬁc kernel I/O object types or to speciﬁed objects or

devices. For additional information, see the vxtrace(1M) manual page.

Using Performance Data

Once performance data has been gathered, it can be used to determine

an optimum system conﬁguration for efﬁcient use of system resources.

The following sections provide an overview of how this data can be used.

Using I/O Statistics

Examination of the I/O statistics can suggest reconﬁguration. There are

two primary statistics: volume I/O activity and disk I/O activity.

Before obtaining statistics, clear (reset) all existing statistics. Use the

vxstat -r utility to clear all statistics. Clearing statistics eliminates any

differences between volumes or disks due to volumes being created, and

also removes statistics from booting (which are not normally of interest).

After clearing the statistics, allow the system to run during typical

system activity. To measure the effect of a particular application or

workload, the system should be run on that particular application or

workload. When monitoring a system that is used for multiple purposes,

try not to exercise any one application more than it would be exercised

normally. When monitoring a time-sharing system with many users, try

to let statistics accumulate during normal use for several hours during

the day.

To display volume statistics, use the vxstat command with no

arguments. The following is an example of output produced using the

vxstat command with no arguments:

OPERATIONS BLOCKS AVG TIME(ms)

TYP NAME READ WRITE READ WRITE READ WRITE

vol archive 865 807 5722 3809 32.5 24.0

vol home 2980 5287 6504 10550 37.7 221.1