If you are mapping the RBD with the kernel driver then you're not using librbd so these settings will have no effect I believe. The kernel driver does its own caching but I don't believe there are any settings to change its default behavior.
On Mon, Feb 29, 2016 at 9:36 PM, Shinobu Kinjo <ski...@redhat.com> wrote: > You may want to set "ioengine=rbd", I guess. > > Cheers, > > ----- Original Message ----- > From: "min fang" <louisfang2...@gmail.com> > To: "ceph-users" <ceph-users@lists.ceph.com> > Sent: Tuesday, March 1, 2016 1:28:54 PM > Subject: [ceph-users] rbd cache did not help improve performance > > Hi, I set the following parameters in ceph.conf > > [client] > rbd cache=true > rbd cache size= 25769803776 > rbd readahead disable after byte=0 > > > map a rbd image to a rbd device then run fio testing on 4k read as the > command > ./fio -filename=/dev/rbd4 -direct=1 -iodepth 64 -thread -rw=read > -ioengine=aio -bs=4K -size=500G -numjobs=32 -runtime=300 -group_reporting > -name=mytest2 > > Compared the result with setting rbd cache=false and enable cache model, I > did not see performance improved by librbd cache. > > Is my setting not right, or it is true that ceph librbd cache will not > have benefit on 4k seq read? > > thanks. > > > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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