Thanks for the detailed response Joe. We're at 256 partition ring size which seems, a little high, but within your guidance.
Jim On 11/6/11 8:10 PM, "Joseph Blomstedt" <j...@basho.com> wrote: >> RE: large ring size warning in the release notes, is the performance >> degradation linear below 256? That is, until the major release that >>fixes >> this, is it best to keep ring sizes at 64 for best performance? > >The large ring size warning in the release notes is predominately >related to an issue with Riak's ring gossip functionality. >Adding/removing nodes, changing bucket properties, and setting cluster >metadata all result in a brief period (usually a few seconds) where >gossip traffic increases significantly. The size of the ring >determines both the number of gossip messages that occur during this >window, as well as the size of each message. With large rings, it is >possible that messages are generated faster than they can be handled, >resulting in large message queues that impact cluster performance and >tie up system memory until the message queues are fully drained. In >general, there is no problem as long as your hardware is fast enough >to process the brief spike in gossip traffic in close to real time. >Concerning this specific issue, choosing a ring size smaller than the >maximum you can handle does not provide any additional performance >gains. > >However, unrelated to this issue, there are general performance >considerations related to ring size versus the number of nodes in your >cluster. Given a fixed number of nodes, a larger ring results in more >vnodes per node. This allows more process concurrency which may >improvement performance. However, each vnode runs it's own backend >instance that has it's own set of on-disk files, and competing >reads/writes to different files may result in additional I/O >contention than having fewer vnodes per node. The overall performance >is going to depend largely on your OS, your file system, and your >traffic pattern. So, it's hard to give specific hard and fast rules. >The other issue is 2I performance. Secondary indexes send request to a >covering set of vnodes, which works out to ring_size / N requests; >therefore increasing the ring_size without increasing N leads to more >2I requests. Again, the right answer depends largely on your use case. > >Overall, I believe we normally recommend between 10 and 50 vnodes per >node, with the ring size rounded up to the next power of two. >Personally, I think 16 vnodes per node is a good number, which matches >the common 64 partition, 4 node Riak cluster. Thus, choosing a ring >size based on that ratio and your expected number of future nodes is a >reasonable choice. Just be sure to stay under 1024 until the issue >with gossip overloading the cluster is resolved. > >-Joe > >On Sat, Nov 5, 2011 at 9:49 AM, Jim Adler <jim.ad...@comcast.net> wrote: >> RE: large ring size warning in the release notes, is the performance >> degradation linear below 256? That is, until the major release that >>fixes >> this, is it best to keep ring sizes at 64 for best performance? >> Jim >> >> Sent from my phone. Please forgive the typos. >> On Nov 4, 2011, at 7:20 PM, Jared Morrow <ja...@basho.com> wrote: >> >> As we've mentioned earlier, the 1.0.2 release of Riak is coming soon. >>Like >> we did with Riak 1.0.0, we are provided a release candidate for test >>before >> we release 1.0.2 final. >> You can find the packages here: >> http://downloads.basho.com/riak/riak-1.0.2rc1/ >> The release notes have been updated and can be found here: >> https://github.com/basho/riak/blob/1.0/RELEASE-NOTES.org >> Thank you, as always, for continuing to provide bug reports and >>feedback. >> -Jared >> >> _______________________________________________ >> riak-users mailing list >> riak-users@lists.basho.com >> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com >> >> _______________________________________________ >> riak-users mailing list >> riak-users@lists.basho.com >> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com >> >> > > > >-- >Joseph Blomstedt <j...@basho.com> >Software Engineer >Basho Technologies, Inc. >http://www.basho.com/ _______________________________________________ riak-users mailing list riak-users@lists.basho.com http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
