Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

■ average operation time (which reflects the total time through the VxVM
interface and is not suitable for comparison against other statistics programs)
These statistics are recorded for logical I/O including reads, writes, atomic copies,
verified reads, verified writes, plex reads, and plex writes for each volume. As a
result, one write to a two-plex volume results in at least five operations: one for
each plex, one for each subdisk, and one for the volume. Also, one read that spans
two subdisks shows at least four reads—one read for each subdisk, one for the
plex, and one for the volume.
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 0 0 0 0 0.0 0.0
vol foobarvol 0 0 0 0 0.0 0.0
vol rootvol 73017 181735 718528 1114227 26.8 27.9
vol swapvol 13197 20252 105569 162009 25.8 397.0
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.
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
Performance monitoring and tuning
Performance monitoring
490