GPA Manual

Using GPA Information
Guardian Performance Analyzer (GPA) Manual—135081
4-12
Disk Volume Performance Analysis
Disk Volume Performance Analysis
To track the performance of the disk volume subsystem, you look at the Disk Volume
Performance section (Example 4-14). Here you can see how the volumes are configured
with respect to primary and backup CPUs as well as primary disk controllers. You can
also see how the volumes compare with regard to a number of performance parameters.
These include request queue time, percentage busy times for the corresponding disk
device and disk I/O process, request rate, cache hit percentage, and cache calls per
request.
Notice in the example that among the volumes with significant activity (that is, a request
rate greater than zero) the volumes $PROD4 and $PROD3 show excessively high
request queue times of 39 and 60 milliseconds respectively. GPA considers any queue
time greater than 25 milliseconds to be excessive.
As the table shows, volumes $PROD4 and $PROD3 are also the most utilized, with far
greater device busy percentages (12.8 and 10.9 percent respectively) than all the others.
However, the high queue times are probably due in large part to the poor cache
performance for these two volumes. As you can see, they show relatively low cache hit
rates of 83.8 and 77.9 percent respectively. GPA further analyzes the cache performance
for all volumes in the next section of its report, as described below.
Cache Performance Analysis
In the Cache Performance Analysis section of the report (Example 4-15), GPA analyzes
the cache performance for each disk volume on the node by the four sizes of blocks,
512, 1024, 2048, and 4096 bytes, used in the system. For each volume and each block
size, the table shows the number of blocks allocated to cache, the percentage of cache
hits, and the number of requests per second.
Example 4-14. Disk Volume Performance Analysis for \NODEB
DISK VOLUME PERFORMANCE ANALYSIS
VOLUME UNT CPU(S) CTL REQUEST AVG PROCESS REQUEST CACHE CACHE
NAME NOS NUM QUEUE DEVICE BUSY% RATE HIT% CALLS PER
P:M PC:BC TIME BUSY% /SECOND REQUEST
-------- --- ----- --- ------- ----- ------- ------- ----- --------
$SYSTEM 0:1 0: 1 %01 0.00 0.11 9.29 78.39 99.8 0.0
$PRODl 0:1 0: 1 %11 1.13 1.47 4.46 35.23 96.4 0.1
$PROD4 2:3 0: 1 %01 39.31 12.84 9.74 8.49 83.8 1.6
$PROD3 0:1 2: 3 %21 60.08 10.93 6.90 6.09 77.9 1.5
$TEST3 2: 2: 3 %21 11.24 2.41 0.83 2.21 93.9 0.9
$PROD5 0:1 2: 3 %31 15.17 1.43 1.13 1.07 96.5 1.0
$PROD2 2:3 2: 3 %31 35.39 1.47 0.34 0.00 0.0 0.6
$TESTl 4: 0: 1 %01 115.42 0.44 0.21 0.00 0.0 0.0
$TEST2 2: 0: 1 %11 52.28 0.00 0.04 0.00 0.0 1.3