Hi Kenneth, I suggested an idea which may help with this, it is being currently being developed .
https://github.com/ceph/ceph/pull/4792 In short there is a high and low threshold with different flushing priorities. Hopefully this will help with bursty workloads. Nick > -----Original Message----- > From: ceph-users [mailto:ceph-users-boun...@lists.ceph.com] On Behalf Of > Kenneth Waegeman > Sent: 02 June 2015 17:54 > To: ceph-users@lists.ceph.com > Subject: [ceph-users] bursty IO, ceph cache pool can not follow evictions > > Hi, > > we were rsync-streaming with 4 cephfs client to a ceph cluster with a cache > layer upon an erasure coded pool. > This was going on for some time, and didn't have real problems. > > Today we added 2 more streams, and very soon we saw some strange > behaviour: > - We are getting blocked requests on our cache pool osds > - our cache pool is often near/ at max ratio > - Our data streams have very bursty IO, (streaming a minute a few hunderds > MB and then nothing) > > Our OSDs are not overloaded (nor the ECs nor cache, checked with iostat), > though it seems like the cache pool can not evict objects in time, and get > blocked until that is ok, each time again. > If I rise the target_max_bytes limit, it starts streaming again until it is full > again. > > cache parameters we have are these: > ceph osd pool set cache hit_set_type bloom ceph osd pool set cache > hit_set_count 1 ceph osd pool set cache hit_set_period 3600 ceph osd pool > set cache target_max_bytes $((14*75*1024*1024*1024)) ceph osd pool set > cache cache_target_dirty_ratio 0.4 ceph osd pool set cache > cache_target_full_ratio 0.8 > > > What can be the issue here ? I tried to find some information about the > 'cache agent' , but can only find some old references.. > > Thank you! > > Kenneth > _______________________________________________ > 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
