write iops drops down after testing for some minutes

Pei Feng Lin <linpeifeng@xxxxxxxxx> · Tue, 8 Mar 2016 10:57:52 +0800

Hi,

I setup a ceph environment with Hammer version. I run benchmark for the rbd image with following command:

fio --ioengine=rbd --pool=performance_test  --rbdname=test1
    --clientname=admin --iodepth=32 --direct=1 
--rw=randwrite --bs=4k  --numjobs=4  --runtime=600 --ramp_time=100 
    --name=test --group_reporting

You can see, 100s warm up and 600s testing ( --runtime=600
      --ramp_time=100 ) are using for the testing. At the first
    300s testing, the write IOPS is stable to 5000. But after 300s
    testing, the write IOPS is not stable, sometimes the high IOPS is up
    to 4500,  the low IOPS drops down to 100. The IOPS jitter is very high,
    and is not stable.

    Does anyone meet the similar issue? How to tune the performance and make it stable?

Thanks!

Peifeng Lin

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