Re: Slow rbd reads (fast writes) with luminous + bluestore

[Emmanuel Lacour <elacour@xxxxxxxxxxxxxxx>]

Le 13/08/2018 à 15:55, Jason Dillaman a écrit :

so problem seems located on "rbd" side  ...

That's a pretty big apples-to-oranges comparison (4KiB random IO to 4MiB full-object IO). With your RBD workload, the OSDs will be seeking after each 4KiB read but w/ your RADOS bench workload, it's reading a full 4MiB object before seeking.

yes you're right, but if we compare cluster to cluser, on new cluster, rados bench is faster (2 times) rbd fio is 7 times slower.

that's why I suppose rbd is th problem here, but I really do not understand how to fix it. I looked at 3 old hammer cluster and two new luminous/buestore clusters and those results are constants. I do not think ceph decided to put bluestore
as default luminous filestore if random reads are 7 time slower ;)


(BTW: thanks for helping me Jason :) ).

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