On Thu, Dec 17, 2015 at 6:16 PM, Florian Haas <flor...@hastexo.com> wrote: > Hey everyone, > > I recently got my hands on a cluster that has been underperforming in > terms of radosgw throughput, averaging about 60 PUTs/s with 70K > objects where a freshly-installed cluster with near-identical > configuration would do about 250 PUTs/s. (Neither of these values are > what I'd consider high throughput, but this is just to give you a feel > about the relative performance hit.) > > Some digging turned up that of the less than 200 buckets in the > cluster, about 40 held in excess of a million objects (1-4M), which > one bucket being an outlier with 45M objects. All buckets were created > post-Hammer, and use 64 index shards. The total number of objects in > radosgw is approx. 160M. > > Now this isn't a large cluster in terms of OSD distribution; there are > only 12 OSDs (after all, we're only talking double-digit terabytes > here). In almost all of these OSDs, the LevelDB omap directory has > grown to a size of 10-20 GB. > > So I have several questions on this: > > - Is it correct to assume that such a large LevelDB would be quite > detrimental to radosgw performance overall? > > - If so, would clearing that one large bucket and distributing the > data over several new buckets reduce the LevelDB size at all? > > - Is there even something akin to "ceph mon compact" for OSDs? > > - Are these large LevelDB databases a simple consequence of having a > combination of many radosgw objects and few OSDs, with the > distribution per-bucket being comparatively irrelevant? > > I do understand that the 45M object bucket itself would have been a > problem pre-Hammer, with no index sharding available. But with what > others have shared here, a rule of thumb of one index shard per > million objects should be a good one to follow, so 64 shards for 45M > objects doesn't strike me as totally off the mark. That's why I think > LevelDB I/O is actually the issue here. But I might be totally wrong; > all insights appreciated. :)
Just giving this one a nudge and CC'ing a few other, presumably interested, parties. :) Ben, Wido, Wade, any thoughts on this one? Cheers, Florian _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
