On 10/30/2014 4:32 AM, Anca Kopetz wrote: > We did some tests with 4 shards / 4 different tomcat instances on the > same server and the average latency was smaller than the one when having > only one shard. > We tested also é shards on different servers and the performance results > were also worse. > > It seems that the sharding does not make any difference for our index in > terms of latency gains.
That statement is confusing, because if latency goes down, that's good, not worse. If you're going to put multiple shards on one server, it should be done with one solr/tomcat instance, not multiple. One instance is perfectly capable of dealing with many shards, and has a lot less overhead. The SolrCloud collection create command would need the maxShardsPerNode parameter. In order to see a gain in performance from multiple shards per server, the server must have a lot of CPUs and the query rate must be fairly low. If the query rate is high, then all the CPUs will be busy just handling simultaneous queries, so putting multiple shards per server will probably slow things down. When query rate is low, multiple CPUs can handle each shard query simultaneously, speeding up the overall query. Thanks, Shawn
