# High I/O read (100%) during query time

**URL:** <https://discuss.elastic.co/t/high-i-o-read-100-during-query-time/48135>\
**Category:** Elasticsearch\
**Created:** [April 22, 2016, 8:08am UTC](https://discuss.elastic.co/t/high-i-o-read-100-during-query-time/48135 "2016-04-22T08:08:41Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![xyz031702](https://avatars.discourse-cdn.com/v4/letter/x/e9c0ed/32.png) [@xyz031702](https://discuss.elastic.co/u/xyz031702)\
**Post date:** [April 22, 2016, 8:08am UTC](https://discuss.elastic.co/t/high-i-o-read-100-during-query-time/48135/1 "2016-04-22T08:08:41Z")

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Hi all,

I installed an ES cluster over 3 servers for some research work:  
(1) Server specs: 32 cores, Intel(R) Xeon(R) CPU E5-2640 v3 @ 2.60GHz, 64G memory,  
(2) 1 primary shard with 2 replica  
(3) JVM with 15G memory allocated. No memory swapping

I'd like to check if any one met a similar problem:  
(1) No concurrent index work  
(2) The query cause 100% I/O usage on all 3 servers!  
(3) while check "iostat". Almost all "i/o read", little "i/o write"  
(4) No other work on the servers  
(5) while check curl 'localhost:9200/\_stats/query\_cache?pretty&human', the cache hit rate is only 8--9%  
(6) The runtime memory cost is about 200m ---1.5G  
(7) elasticsearch.yml is configured:

> threadpool.index.type: fixed  
> threadpool.index.queue\_size: 1000  
> threadpool.bulk.queue\_size: 1000  
> threadpool.search.queue\_size: 3000  
> bootstrap.mlockall: true  
> index.cache.field.type: soft  
> index.cache.field.expire: 10m  
> index.cache.field.max\_size: 50000  
> indices.cache.query.size: 5%  
> indices.cache.filter.size: 10gb  
> indices.fielddata.cache.size: 10gb

The queries have been simplified: search a keyword with a boolquery, without any filters, without any sort, without calculation any distances

The query time may take up to 10 seconds in peak hours. Normal time cost is about 50--500ms

Would great appreciate if anyone could share hints on this issue.

Best regards,  
Ding

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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:** [July 5, 2017, 10:57pm UTC](https://discuss.elastic.co/t/high-i-o-read-100-during-query-time/48135/2 "2017-07-05T22:57:05Z")

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Closed on July 5, 2017, 10:57pm UTC