# Optimize server performance

**URL:** <https://discuss.elastic.co/t/optimize-server-performance/195657>\
**Category:** Elasticsearch\
**Created:** [August 18, 2019, 4:42pm UTC](https://discuss.elastic.co/t/optimize-server-performance/195657 "2019-08-18T16:42:12Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![jgimenez](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jgimenez/32/34681_2.png) [@jgimenez](https://discuss.elastic.co/u/jgimenez)\
**Post date:** [August 18, 2019, 4:42pm UTC](https://discuss.elastic.co/t/optimize-server-performance/195657/1 "2019-08-18T16:42:12Z")

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Hi, I'm running an Elasticsearch cluster and I'm not sure we're maximizing the usage of server resources. When bulk-indexing at maximum speed, CPU, disk I/O and garbage collection seem all pretty low, yet Elasticsearch rejects new bulk requests because the thread pool is full. I'm suspecting the limit might be on some configuration setting. Any ideas on which resource to look up or which setting to tweak to see if performance can be improved? Basically, find out what's the bottleneck? Thanks!

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**Author:** ![wangqinghuan](https://avatars.discourse-cdn.com/v4/letter/w/d26b3c/32.png) [@wangqinghuan](https://discuss.elastic.co/u/wangqinghuan)\
**Post date:** [August 18, 2019, 5:09pm UTC](https://discuss.elastic.co/t/optimize-server-performance/195657/2 "2019-08-18T17:09:28Z")

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hi  
[https://www.elastic.co/cn/blog/why-am-i-seeing-bulk-rejections-in-my-elasticsearch-cluster](https://www.elastic.co/cn/blog/why-am-i-seeing-bulk-rejections-in-my-elasticsearch-cluster) This can help you.

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**Author:** ![DavidTurner](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/davidturner/32/22453_2.png) [@DavidTurner](https://discuss.elastic.co/u/DavidTurner)\
**Post date:** [August 26, 2019, 2:18pm UTC](https://discuss.elastic.co/t/optimize-server-performance/195657/3 "2019-08-26T14:18:44Z")

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I'd also try looking at the [hot threads API](https://www.elastic.co/guide/en/elasticsearch/reference/current/cluster-nodes-hot-threads.html) to see what it's so busy doing. For instance, if the bottleneck is slow IO then you might see low CPU and low disk IO, but you may see lots of threads waiting on IO operations, particularly things like a `force()` (i.e. a `fsync()` call).

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**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [September 23, 2019, 2:18pm UTC](https://discuss.elastic.co/t/optimize-server-performance/195657/4 "2019-09-23T14:18:44Z")

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