Chapter 6. Diagnostics and performance monitoring 81
Figure 6-14 The lsess command output
Figure 6-15 shows the output from the lsdd command.
Figure 6-15 The lssdd command output
6.2.3 AIX diagnostic tools
The AIX operating system provides a number of tools that can be used to view system
activity. We will describe here the most commonly used ones.
iostat
From an AIX operating system perspective, the best tool for investigating I/O performance is
iostat. With this tool you can monitor I/O statistics at both the individual hdisk level and
aggregated. The output indicates how active your CPUs are as they issue I/O commands and
wait for their completion, and you can view the performance of each ESS logical disk.
Figure 6-16 is output from a typical iostat listing.
Disk Location LUN SN Type Size LSS Vol Rank S Connection
------ ------------ -------- ------------ ---- --- --- ---- - -----------
hdisk114 B0-60-01[FC] 60617733 IBM 2105-F20 12.6 22 6 1600 04 Y
hdisk115 B0-60-01[FC] 60817733 IBM 2105-F20 12.6 22 8 1601 04 Y
hdisk116 B0-60-01[FC] 60A17733 IBM 2105-F20 12.6 22 10 1602 04 Y
hdisk117 B0-60-01[FC] 60C17733 IBM 2105-F20 12.6 22 12 1603 04 Y
hdisk118 B0-60-01[FC] 60E17733 IBM 2105-F20 12.6 22 14 1604 04 Y
hdisk119 B0-60-01[FC] 61017733 IBM 2105-F20 12.6 22 16 1605 04 Y
Hostname VG vpath hdisk Location LUN SN S Connection Size LSS Vol Rank
-------- -- ----- ----- -------- ------ - ---------- ---- --- --- ----
bigbluebox essdatavg1 vpath0 hdisk60 B0-60-01 00117733 Y R1-B1-H4-ZA 122.7 16 1 1001
bigbluebox essdatavg1 vpath0 hdisk186 30-60-01 00117733 Y R1-B2-H4-ZA 122.7 16 1 1001
bigbluebox essdatavg1 vpath0 hdisk312 90-60-01 00117733 Y R1-B4-H4-ZA 122.7 16 1 1001
bigbluebox essdatavg1 vpath1 hdisk61 B0-60-01 00017733 Y R1-B1-H4-ZA 105.2 16 0 1000
bigbluebox essdatavg1 vpath1 hdisk187 30-60-01 00017733 Y R1-B2-H4-ZA 105.2 16 0 1000
bigbluebox essdatavg1 vpath1 hdisk313 90-60-01 00017733 Y R1-B4-H4-ZA 105.2 16 0 1000
bigbluebox essda3vg1 vpath2 hdisk62 B0-60-01 20017733 Y R1-B1-H4-ZA 50.4 18 0 1202
bigbluebox essda3vg1 vpath2 hdisk188 30-60-01 20017733 Y R1-B2-H4-ZA 50.4 18 0 1202
bigbluebox essda3vg1 vpath2 hdisk314 90-60-01 20017733 Y R1-B4-H4-ZA 50.4 18 0 1202
82 IBM ESS and IBM DB2 UDB Working Together
Figure 6-16 A sample iostat listing
The first group of output lines is a summary of all activity since the last system boot. The
remaining lines are grouped by each time interval measured.
If you are using multipathing, the true statistic for a particular ESS logical disk will be the sum
of the numbers for every AIX system hdisk that is mapped to the ESS logical disk. That is, the
figures returned by iostat are for each path to the ESS logical disk, not the logical disk itself.
As explained in the Mapping chapter, you will need to use the lsvpcfg command to determine
which hdisks to summarize for a particular ESS logical disk. For instance, assuming that the
three hdisks reported in Figure 6-16 are the hdisks comprising a single vpath, vpath102, we
could interpret the output as shown in Figure 6-17.
Figure 6-17 Interpreted iostat listing for two disks associated with a single vpath
Note that with a RAID5 implementation, a value of 100 in the % tm_act column of the iostat
output does not mean that the RAID array physical disks are 100% busy. This column is the
iostats interpretation of the percent of time the individual path to the ESS logical volume is
busy.
>iostat -d hdisk288 hdisk414 hdisk162 30 5
Disks: % tm_act Kbps tps Kb_read Kb_wrtn
hdisk288 5.1 454.3 6.7 12042630 9143565
hdisk414 5.1 449.0 6.7 11883078 9054305
hdisk162 5.0 505.3 7.4 13762027 9799044
hdisk288 50.3 3611.0 164.4 33336 75004
hdisk414 47.8 3457.7 162.2 29492 74248
hdisk162 46.1 3765.6 176.3 31676 81304
hdisk288 32.9 2352.5 119.9 15160 55420
hdisk414 27.3 2108.4 111.9 11132 52124
hdisk162 30.1 2442.4 119.6 18352 54924
hdisk288 17.5 1146.6 70.2 920 33480
hdisk414 17.2 1231.1 76.5 384 36552
hdisk162 13.9 1009.5 61.6 1084 29204
hdisk288 25.6 1882.6 74.1 8 56476
hdisk414 26.2 1937.6 75.9 4 58128
hdisk162 25.0 2007.6 82.7 8 60224
Disks: % tm_act Kbps tps Kb_read Kb_wrtn
hdisk288 5.1 454.3 6.7 12042630 9143565
hdisk414 5.1 449.0 6.7 11883078 9054305
hdisk162 5.0 505.3 7.4 13762027 9799044
vpath102: ---- 1408.6 20.8 37687735 27996914
hdisk288 50.3 3611.0 164.4 33336 75004
hdisk414 47.8 3457.7 162.2 29492 74248
hdisk162 46.1 3765.6 176.3 31676 81304
vpath102: ---- 10834.3 502.9 94504 230556
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