# ES 1.4.2 Performance Issue **URL:** \ **Category:** Elasticsearch\ **Created:** [September 8, 2015, 10:15am UTC](https://discuss.elastic.co/t/es-1-4-2-performance-issue/28831 "2015-09-08T10:15:35Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Hagai\_T](https://avatars.discourse-cdn.com/v4/letter/h/b9e5f3/32.png) [@Hagai\_T](https://discuss.elastic.co/u/Hagai_T)\ **Post date:** [September 8, 2015, 10:15am UTC](https://discuss.elastic.co/t/es-1-4-2-performance-issue/28831/1 "2015-09-08T10:15:35Z")
Hi, I have 8 nodes cluster running over Amazon AWS. 2 Master/Client nodes and 6 Data Nodes (each data node has 16 cores and 64GB of RAM - c4.4xlarge) Elasticsearch version: is 1.4.2, OS: Amazon AMI In the last few days the CPU usage of the data nodes increased dramatically (from 20%-40% to 80%-100%) causing very slow searches. Elasticsearch process is the one that consumes all of the CPU resources. I performed the hot threads command as following: http://:9200/\_nodes/hot\_threads and here is the output: > Your help is much appreciated. Thanks, Hagai. ---
**Author:** ![lzerma](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/lzerma/32/4661_2.png) [@lzerma](https://discuss.elastic.co/u/lzerma)\ **Post date:** [September 9, 2015, 1:42pm UTC](https://discuss.elastic.co/t/es-1-4-2-performance-issue/28831/2 "2015-09-09T13:42:37Z")
Hi, I think, seeing your hot threads dump, may be the problem could be the merging segments. Take a look on this [link](https://www.elastic.co/guide/en/elasticsearch/guide/current/merge-process.html). As far as are you performing some update every time? I mean, there are concurrently process running, like searching and bulk indexing when the CPU come up to 100%? ---
**Author:** ![warkolm](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/warkolm/32/39224_2.png) [@warkolm](https://discuss.elastic.co/u/warkolm)\ **Post date:** [September 10, 2015, 5:58am UTC](https://discuss.elastic.co/t/es-1-4-2-performance-issue/28831/3 "2015-09-10T05:58:51Z")
Also - we recommend 3 master nodes, otherwise you run a risk of split brain as you never have a majority quorum. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [July 5, 2017, 11:51pm UTC](https://discuss.elastic.co/t/es-1-4-2-performance-issue/28831/4 "2017-07-05T23:51:24Z")