VERITAS Volume Manager 3.5 Administrator's Guide (September 2004)

Performance Monitoring and Tuning

Performance Monitoring

Chapter 12 393

VxVM also maintains other statistical data. For each plex, it records read

and write failures. For volumes, it records corrected read and write

failures in addition to read and write failures.

To reset the statistics information to zero, use the -r option. This can be

done for all objects or for only those objects that are speciﬁed. Resetting

just prior to an operation makes it possible to measure the impact of that

particular operation.

The following is an example of output produced using the vxstat

command:

OPERATIONS BLOCKS AVG TIME(ms)

TYP NAME READ WRITE READ WRITE READ WRITE

vol blop 00000.00.0

vol foobarvol 00000.00.0

vol rootvol 73017 181735 718528 1114227 26.8 27.9

vol swapvol 13197 20252 105569 162009 25.8 397.0

vol testvol 00000.00.0

Additional volume statistics are available for RAID-5 conﬁgurations.

For detailed information about how to use vxstat, refer to the vxstat

(1M) manual page.

Using Performance Data

When you have gathered performance data, you can use it to determine

how to conﬁgure your system to use resources most effectively. The

following sections provide an overview of how you can use this data.

Using I/O Statistics

Examination of the I/O statistics can suggest how to reconﬁgure your

system. You should examine two primary statistics: volume I/O activity

and disk I/O activity.

Before obtaining statistics, reset the counters for all existing statistics

using the vxstat -r command. This eliminates any differences between

volumes or disks due to volumes being created, and also removes

statistics from boot time (which are not usually of interest).

After resetting the counters, allow the system to run during typical

system activity. Run the application or workload of interest on the

system to measure its effect. When monitoring a system that is used for