Veritas Volume Manager 5.0 Administrator's Guide (September 2006)
457Performance monitoring and tuning
Performance monitoring
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 multiple purposes, try not to exercise any one
application more than usual. When monitoring a time-sharing system with many users, let
statistics accumulate for several hours during the normal working day.
To display volume statistics, enter the
vxstat command with no arguments. The
following is a typical display of volume statistics:
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
vol local 49477 49230 507892 204975 28.5 33.5
vol rootvol 102906 342664 1085520 1962946 28.1 25.6
vol src 79174 23603 425472 139302 22.4 30.9
vol swapvol 22751 32364 182001 258905 25.3 323.2
Such output helps to identify volumes with an unusually large number of operations or
excessive read or write times.
To display disk statistics, use the vxstat -d command. The following is a typical display
of disk statistics:
OPERATIONS BLOCKS AVG TIME(ms)
TYP NAME READ WRITE READ WRITE READ WRITE
dm mydg01 40473 174045 455898 951379 29.5 35.4
dm mydg02 32668 16873 470337 351351 35.2 102.9
dm mydg03 55249 60043 780779 731979 35.3 61.2
dm mydg04 11909 13745 114508 128605 25.0 30.7
If you need to move the volume named archive onto another disk, use the following
command to identify on which disks it lies:
# vxprint -g mydg -tvh archive
The following is an extract from typical output:
V NAME RVG/VSET/CO KSTATE STATE LENGTH READPOL REFPLEX UTYPE
PL NAME VOLUME KSTATE STATE LENGTH LAYOUT NCOL/WDTH MODE
SD NAME PLEX DISK DISKOFFS LENGTH [COL/]OFF DEVICE MODE
v archive - ENABLED ACTIVE 20480 SELECT - fsgen
pl archive-01 archive ENABLED ACTIVE 20480 CONCAT - RW
sd mydg03-03 archive-01 mydg03 0 40960 0 c1t2d0 ENA