Riak 1.0.2 RC1

Jim Adler jim.adler at comcast.net
Mon Nov 7 09:23:28 EST 2011


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" <joe at 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.adler at 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 <jared at 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
>>
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>
>
>
>-- 
>Joseph Blomstedt <joe at basho.com>
>Software Engineer
>Basho Technologies, Inc.
>http://www.basho.com/






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