On 07/09/2014 05:57 AM, Xabier Elkano wrote: > > > Hi, > > I was doing some tests in my cluster with fio tool, one fio instance > with 70 jobs, each job writing 1GB random with 4K block size. I did this > test with 3 variations: > > 1- Creating 70 images, 60GB each, in the pool. Using rbd kernel module, > format and mount each image as ext4. Each fio job writing in a separate > image/directory. (ioengine=libaio, queue_depth=4, direct=1) > > IOPS: 6542 > AVG LAT: 41ms > > 2- Creating 1 large image 4,2TB in the pool. Using rbd kernel module, > format and mount the image as ext4. Each fio job writing in a separate > file in the same directory. (ioengine=libaio, queue_depth=4,direct=1) > > IOPS: 5899 > AVG LAT: 47ms > > 3- Creating 1 large image 4,2TB in the pool. Use ioengine rbd in fio to > access the image through librados. (ioengine=rbd, queue_depth=4,direct=1) > > IOPS: 2638 > AVG LAT: 96ms > > Do these results make sense? From Ceph perspective, It is better to have > many small images than a larger one? What is the best approach to > simulate the workload of 70 VMs? I'm not sure the difference between the first two cases is enough to say much yet. You may need to repeat the test a couple of times to ensure that the difference is more than noise. having said that, if we are seeing an effect, it would be interesting to know what the latency distribution is like. is it consistently worse in the 2nd case or do we see higher spikes at specific times? In case 3, do you have multiple fio jobs going or just 1? > > > thanks in advance or any help, > Xabier > _______________________________________________ > ceph-users mailing list > ceph-users at lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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