Hi guys,

So recently I was testing our ceph cluster which mainly used for block 
usage(rbd).

We have 30 ssd drives total(5 storage nodes,6 ssd drives each node).However the 
result of fio is very poor.

We tested the workload on ssd pool with following parameter :

"fio --size=50G \

       --ioengine=rbd \

       --direct=1 \

       --numjobs=1 \

       --rw=randwrite(randread) \

       --name=com_ssd_4k_randwrite(randread) \

       --bs=4k \

       --iodepth=32 \

       --pool=ssd_volumes \

       --runtime=60 \

       --ramp_time=30 \

--rbdname=4k_test_image"

and here is the result:

random write:4631;random read:21127 




I also tested  the pool(size=1,min_size=1,pg_num=256) which is consisted by  
only one single ssd drive with same workload pattern which is more 
acceptable.(random write:8303;random read:27859)




We have optimized the linux kernal(read_ahead,disk_scheduler,numa,swappiness) 
and ceph.conf(client_message,filestore_queue,journal_queue,rbd_cache).And 
checked the raid cache setting.




The only deficiency for the architecture is the unbalance weight between three 
racks which one rack has only one storage node.




So can anybody tell us whether  this  number is reasonable.If not,any 
suggestion to improve the number will be appreciated.




 























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