# About segment merge **URL:** \ **Category:** Elasticsearch\ **Created:** [September 13, 2017, 7:27am UTC](https://discuss.elastic.co/t/about-segment-merge/100299 "2017-09-13T07:27:24Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![elton](https://avatars.discourse-cdn.com/v4/letter/e/eada6e/32.png) [@elton](https://discuss.elastic.co/u/elton)\ **Post date:** [September 13, 2017, 7:27am UTC](https://discuss.elastic.co/t/about-segment-merge/100299/1 "2017-09-13T07:27:24Z")
Hello, I have a heavily indexed elasticsearch cluster, about 20K lines per second, and one index per day. Each index has about 300 segments. For example, segment info of some index (2017-08-19) is partially list below: > Blockquote > index shard prirep ip segment generation docs.count docs.deleted size size.memory committed searchable version compound > qn\_2017-08-19 0 r 10.2.93.185 \_2vsr 134523 35865749 0 5gb 9752042 true true 6.5.1 false > qn\_2017-08-19 0 r 10.2.93.185 \_4n3y 216574 34562168 0 5gb 9048328 true true 6.5.1 false > qn\_2017-08-19 0 r 10.2.93.185 \_637c 284088 34114706 0 5gb 9499344 true true 6.5.1 false > qn\_2017-08-19 0 r 10.2.93.185 \_661v 287779 2481838 0 380.7mb 791589 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_68fs 290872 1336373 0 198.7mb 419710 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6af6 293442 828156 0 121mb 279891 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6c1p 295549 1731130 0 254.9mb 515564 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6eaf 298455 942425 0 137.2mb 285555 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6gp9 301581 2502974 0 373.1mb 748680 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6j0o 304584 385143 0 56.9mb 146525 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6jqq 305522 927247 0 134.6mb 268981 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6ly0 308376 1776647 0 259.9mb 493364 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6md9 308925 76160 0 11.4mb 42011 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6mgj 309043 294887 0 43.3mb 108513 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6mwz 309635 243215 0 34.6mb 102228 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6nd4 310216 118901 0 17.7mb 54620 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6nkl 310485 248982 0 36.1mb 110568 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6nvy 310894 126586 0 18.4mb 58437 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6o3s 311176 135339 0 19.8mb 62553 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6ocz 311507 273520 0 39.9mb 103114 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6onk 311888 72061 0 10.7mb 38558 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6oqn 311999 53366 0 8mb 34997 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6oto 312108 100517 0 14.9mb 45692 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6oy4 312268 44420 0 6.7mb 30418 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6oz4 312304 34652 0 5.2mb 27141 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6oz5 312305 3 0 5.6kb 2466 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6oz6 312306 10 0 8.8kb 4248 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6oz7 312307 1 0 5.6kb 2706 true true 6.5.1 true > qn\_2017-08-19 0 r 10.2.93.185 \_6oz8 312308 1 0 5.5kb 2825 true true 6.5.1 true > qn\_2017-08-19 0 p 10.2.93.205 \_2vsr 134523 35865749 0 5gb 9752042 true true 6.5.1 false > qn\_2017-08-19 0 p 10.2.93.205 \_4n3y 216574 34562168 0 5gb 9048328 true true 6.5.1 false > qn\_2017-08-19 0 p 10.2.93.205 \_637c 284088 34114706 0 5gb 9499344 true true 6.5.1 false > qn\_2017-08-19 0 p 10.2.93.205 \_661v 287779 2481838 0 380.7mb 791589 true true 6.5.1 true > qn\_2017-08-19 0 p 10.2.93.205 \_68fs 290872 1336373 0 198.7mb 419710 true true 6.5.1 true > qn\_2017-08-19 0 p 10.2.93.205 \_6af6 293442 828156 0 121mb 279891 true true 6.5.1 true > qn\_2017-08-19 0 p 10.2.93.205 \_6c1p 295549 1731130 0 254.9mb 515564 true true 6.5.1 true > qn\_2017-08-19 0 p 10.2.93.205 \_6eaf 298455 942425 0 137.2mb 285555 true true 6.5.1 true > qn\_2017-08-19 0 p 10.2.93.205 \_6gp9 301581 2502974 0 373.1mb 748680 true true 6.5.1 true > qn\_2017-08-19 0 p 10.2.93.205 \_6j0o 304584 385143 0 56.9mb 146525 true true 6.5.1 true > qn\_2017-08-19 0 p 10.2.93.205 \_6jqq 305522 927247 0 134.6mb 268981 true true 6.5.1 true > qn\_2017-08-19 0 p 10.2.93.205 \_6ly0 308376 1776647 0 259.9mb 493364 true true 6.5.1 true As we can see, there are some very small segments. However, after I trigger a force merge, no merge is done. My question is why force merge is not done? Thanks a lot 😃 ---
**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\ **Post date:** [September 13, 2017, 8:18am UTC](https://discuss.elastic.co/t/about-segment-merge/100299/2 "2017-09-13T08:18:31Z")
How did you run the force merge? Did you set [max\_num\_segments](https://www.elastic.co/guide/en/elasticsearch/reference/5.6/indices-forcemerge.html#forcemerge-parameters) to 1? ---
**Author:** ![elton](https://avatars.discourse-cdn.com/v4/letter/e/eada6e/32.png) [@elton](https://discuss.elastic.co/u/elton)\ **Post date:** [September 13, 2017, 9:01am UTC](https://discuss.elastic.co/t/about-segment-merge/100299/3 "2017-09-13T09:01:59Z")
yes, I tried different max\_num\_segments, for example 1, 10, 100. Doesn't work. ---
**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\ **Post date:** [September 13, 2017, 9:04am UTC](https://discuss.elastic.co/t/about-segment-merge/100299/4 "2017-09-13T09:04:11Z")
Which version of Elasticsearch are you on? Is there anything in the logs? ---
**Author:** ![elton](https://avatars.discourse-cdn.com/v4/letter/e/eada6e/32.png) [@elton](https://discuss.elastic.co/u/elton)\ **Post date:** [September 13, 2017, 9:14am UTC](https://discuss.elastic.co/t/about-segment-merge/100299/5 "2017-09-13T09:14:14Z")
My elasticsearch is 5.4.3, nothing special in my log. When trigger a force merge, curl return immediately. > Blockquote > curl -XPOST [http://ip](http://ip):port/qn\_2017-08-19/\_forcemerge > {"\_shards":{"total":10,"successful":10,"failed":0}} I tried to do force merge other indices which are very small only containing thousands of docs, the force merge works. And curl waits until merge is done. ---
**Author:** ![elton](https://avatars.discourse-cdn.com/v4/letter/e/eada6e/32.png) [@elton](https://discuss.elastic.co/u/elton)\ **Post date:** [September 13, 2017, 9:19am UTC](https://discuss.elastic.co/t/about-segment-merge/100299/6 "2017-09-13T09:19:55Z")
This issue confuses me for a long time. I tried to do force merge to improve search performance and save some file handles. I google misc docs, such as index throttle, merge scheduler. Looks like they are not related to my issue. ---
**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\ **Post date:** [September 13, 2017, 9:26am UTC](https://discuss.elastic.co/t/about-segment-merge/100299/7 "2017-09-13T09:26:02Z")
In your example you are not specifying `max_num_segments`. If you do this on the index you showed before, how long does it take for it to return? ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [October 11, 2017, 9:26am UTC](https://discuss.elastic.co/t/about-segment-merge/100299/8 "2017-10-11T09:26:07Z")
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