I never played much with rados bench but it doesn't seem to have for example settings for synchronous/asynchronous workloads, thus it probably just benchmarks the OSD throughput and ability to write to journal (in write mode) unless you let it run for a longer time. So when you stop rados bench the OSDs are actually still flushing the data, exactly as you wrote.
There are parameters filestore_min_sync_interval and filestore_max_sync_interval on OSDs, the cluster should be idle after filestore_max_sync_interval (+ a few seconds to actually write the dirty data + possibly a few seconds for filesystem to flush) has elapsed. How did you drop caches on the OSD nodes? I apologize in advance if I'm wrong :-) Jan > On 08 Sep 2015, at 20:38, Deneau, Tom <[email protected]> wrote: > > When measuring read bandwidth using rados bench, I've been doing the > following: > * write some objects using rados bench write --no-cleanup > * drop caches on the osd nodes > * use rados bench seq to read. > > I've noticed that on the first rados bench seq immediately following the > rados bench write, > there is often activity on the journal partitions which must be a carry over > from the rados > bench write. > > What is the preferred way to ensure that all write activity is finished > before starting > to use rados bench seq? > > -- Tom Deneau > > _______________________________________________ > ceph-users mailing list > [email protected] > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list [email protected] http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
