# Performance and preference \_local **URL:** \ **Category:** Elasticsearch\ **Created:** [August 3, 2011, 5:45pm UTC](https://discuss.elastic.co/t/performance-and-preference--local/5047 "2011-08-03T17:45:48Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Ridvan\_Gyundogan](https://avatars.discourse-cdn.com/v4/letter/r/e495f1/32.png) [@Ridvan\_Gyundogan](https://discuss.elastic.co/u/Ridvan_Gyundogan)\ **Post date:** [August 3, 2011, 5:45pm UTC](https://discuss.elastic.co/t/performance-and-preference--local/5047/1 "2011-08-03T17:45:48Z")
Hi, I do some performance tests and have some questions regarding this. Our architecture for the tests is very simple we have ec2 image containing ES 16.2 and tomcat. The data for the ES is stored in s3 gateway - only 6k documents. The tomcat makes search requests to the local ES instance and returns the response to jmetter. No communication between the tomcats. We have 1 index with 5 shards and 1 replica. When doing tests against 1 ec2 instance we are stable at 80 jmetter threads. When doing the tests against 2 ec2 instances we are stable at 140 threads. Going to 160 threads leads to timeout errors. We use searchRequestBuilder.setPreference("\_local") before each request. My expectations are that if each of the ec2 instances has all the shards or their replicas there should not be communication between the 2 ES nodes for the search requests. So we should be stable at 160 threads or not? Do you know how to check whether there is ore there is no network traffic between the 2 ES nodes related to the search requests? ---
**Author:** ![Ridvan\_Gyundogan](https://avatars.discourse-cdn.com/v4/letter/r/e495f1/32.png) [@Ridvan\_Gyundogan](https://discuss.elastic.co/u/Ridvan_Gyundogan)\ **Post date:** [August 4, 2011, 2:05pm UTC](https://discuss.elastic.co/t/performance-and-preference--local/5047/2 "2011-08-04T14:05:03Z")
To add something to this: when under load if I search for the count of the open files from the es server i see that the second server which is supposed to be the replica has 2 times the open files of the first server which holds the primary shards. Any idea? On Aug 3, 8:45 pm, Ridvan Gyundogan [ridva...@gmail.com](mailto:ridva...@gmail.com) wrote: > Hi, > I do some performance tests and have some questions regarding this. > Our architecture for the tests is very simple we have ec2 image > containing ES 16.2 and tomcat. > The data for the ES is stored in s3 gateway - only 6k documents. > > The tomcat makes search requests to the local ES instance and returns > the response to jmetter. No communication between the tomcats. > > We have 1 index with 5 shards and 1 replica. > > When doing tests against 1 ec2 instance we are stable at 80 jmetter > threads. > > When doing the tests against 2 ec2 instances we are stable at 140 > threads. Going to 160 threads leads to timeout errors. We use > searchRequestBuilder.setPreference("\_local") before each request. > > My expectations are that if each of the ec2 instances has all the > shards or their replicas there should not be communication between the > 2 ES nodes for the search requests. So we should be stable at 160 > threads or not? > > Do you know how to check whether there is ore there is no network > traffic between the 2 ES nodes related to the search requests? ---
**Author:** ![kimchy](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/kimchy/32/44952_2.png) [@kimchy](https://discuss.elastic.co/u/kimchy)\ **Post date:** [August 5, 2011, 7:58pm UTC](https://discuss.elastic.co/t/performance-and-preference--local/5047/3 "2011-08-05T19:58:19Z")
When you set the preference to local, then if it can, it will prefer execution on the local node, yes, but, I don't think that thats what will help your case. Regarding hte number of open files, they can be different between nodes. The fact that they have more or less primary shards is not relevant, they might simply be on a different merge state of the index (the internal optimization that goes on). I would check a few things in your case: First, check that jmeter is not going through memory problems. Also, I found that jmeter is not behaving properly with many threads executing, I suspect that its because of bad concurrency implementation on the stats data structures it has. Second, see that you don't overflow the system. Check if you get into big iowait, check the load, and the likes. Also, on AWS, you might end up being on the same machine where netflix is busy transcoding inception or something... On Thu, Aug 4, 2011 at 5:05 PM, Ridvan Gyundogan [ridvansg@gmail.com](mailto:ridvansg@gmail.com) wrote: > To add something to this: > when under load if I search for the count of the open files from the > es server i see that the second server which is supposed to be the > replica has 2 times the open files of the first server which holds the > primary shards. Any idea? > > On Aug 3, 8:45 pm, Ridvan Gyundogan [ridva...@gmail.com](mailto:ridva...@gmail.com) wrote: > > > Hi, > > I do some performance tests and have some questions regarding this. > > Our architecture for the tests is very simple we have ec2 image > > containing ES 16.2 and tomcat. > > The data for the ES is stored in s3 gateway - only 6k documents. > > > > The tomcat makes search requests to the local ES instance and returns > > the response to jmetter. No communication between the tomcats. > > > > We have 1 index with 5 shards and 1 replica. > > > > When doing tests against 1 ec2 instance we are stable at 80 jmetter > > threads. > > > > When doing the tests against 2 ec2 instances we are stable at 140 > > threads. Going to 160 threads leads to timeout errors. We use > > searchRequestBuilder.setPreference("\_local") before each request. > > > > My expectations are that if each of the ec2 instances has all the > > shards or their replicas there should not be communication between the > > 2 ES nodes for the search requests. So we should be stable at 160 > > threads or not? > > > > Do you know how to check whether there is ore there is no network > > traffic between the 2 ES nodes related to the search requests? ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [July 6, 2017, 3:58am UTC](https://discuss.elastic.co/t/performance-and-preference--local/5047/4 "2017-07-06T03:58:08Z")