DS5100 random IO performance on DMP by default is not as good as that on the MPIO.
Article ID: 100004673
Updated On:
Cause
queue_depth 1 is too low for the array, which limits the performance much.
Below is the testing result about the queue_depth.
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The volume configuration:-
#vxdmpadm getsubpaths dmpnodename=ds51000_94
NAME STATE[A] PATH-TYPE[M] CTLR-NAME ENCLR-TYPE ENCLR-NAME ATTRS
================================================================================
hdisk284 ENABLED SECONDARY fscsi2 DS5100 ds51000 -
hdisk385 ENABLED(A) PRIMARY fscsi3 DS5100 ds51000 -
#vxprint -ht -q
Disk group: testdg
dg testdg default default 7000 1294945920.109.p550a7
dm ds51000_94 ds51000_94 auto 65536 2023168 -
v vol1 - ENABLED ACTIVE 1843200 SELECT - fsgen
pl vol1-01 vol1 ENABLED ACTIVE 1843200 CONCAT - RW
sd ds51000_94-01 vol1-01 ds51000_94 0 1843200 0 ds51000_94 ENA
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Use vxbench to test random read throughput continuously.
e.g.
while true
do
/opt/VRTSspt/FS/VxBench/vxbench -w rand_read -o sync -i maxfilesize=512m,nthreads=50,iosize=8k,nrep=3200 /dev/vx/dsk/testdg/vol1
done
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Test result with the default queue_depth.
#lsattr -El hdisk385|grep queue_depth
queue_depth 1 Queue DEPTH True
Run the above vxbench.
total: 21.016 sec 12181.25 KB/s cpu: 13.35 sys 1.67 user
total: 21.176 sec 12089.22 KB/s cpu: 13.30 sys 1.66 user
total: 21.197 sec 12077.00 KB/s cpu: 13.35 sys 1.67 user
total: 21.189 sec 12081.98 KB/s cpu: 13.29 sys 1.66 user
total: 21.385 sec 11971.28 KB/s cpu: 13.28 sys 1.66 user
total: 21.226 sec 12060.89 KB/s cpu: 13.35 sys 1.67 user
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Test result with queue_depth 10.
#lsattr -El hdisk385|grep queue_depth
queue_depth 10 Queue DEPTH True
Run the above vxbench.
total: 1.290 sec 198448.54 KB/s cpu: 0.93 sys 0.14 user
total: 1.290 sec 198432.69 KB/s cpu: 0.92 sys 0.14 user
total: 1.290 sec 198509.17 KB/s cpu: 0.93 sys 0.15 user
total: 1.290 sec 198472.69 KB/s cpu: 0.93 sys 0.14 user
total: 1.290 sec 198440.38 KB/s cpu: 0.92 sys 0.14 user
total: 1.290 sec 198437.92 KB/s cpu: 0.94 sys 0.15 user
total: 1.290 sec 198506.24 KB/s cpu: 0.93 sys 0.14 user
total: 1.290 sec 198419.93 KB/s cpu: 0.94 sys 0.15 user
<= the IO throughput was increased significantly, and the CPU cost was dropped.
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Resolution
Increase the queue_depth to 10 or above.
#chdev –l hdisk385 -a queue_depth=10 -P
Please note, reboot is required to make the changes effective.
Applies To
The AIX server with DS5100 attached.
Issue/Introduction
