# Elasticsearch Index writes is really do flush() or synch() at OS level

**URL:** <https://discuss.elastic.co/t/elasticsearch-index-writes-is-really-do-flush-or-synch-at-os-level/188005>\
**Category:** Elasticsearch\
**Created:** [June 28, 2019, 9:34am UTC](https://discuss.elastic.co/t/elasticsearch-index-writes-is-really-do-flush-or-synch-at-os-level/188005 "2019-06-28T09:34:35Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![suvarna](https://avatars.discourse-cdn.com/v4/letter/s/51bf81/32.png) [@suvarna](https://discuss.elastic.co/u/suvarna)\
**Post date:** [June 28, 2019, 9:34am UTC](https://discuss.elastic.co/t/elasticsearch-index-writes-is-really-do-flush-or-synch-at-os-level/188005/1 "2019-06-28T09:34:35Z")

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Hi

Can you please let me whether Elasticsearch Index writes is really do flush() or synch() at OS level

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**Author:** ![dadoonet](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dadoonet/32/137187_2.png) [@dadoonet](https://discuss.elastic.co/u/dadoonet)\
**Post date:** [June 28, 2019, 11:01am UTC](https://discuss.elastic.co/t/elasticsearch-index-writes-is-really-do-flush-or-synch-at-os-level/188005/2 "2019-06-28T11:01:18Z")

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It is true for the transaction log.

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**Author:** ![suvarna](https://avatars.discourse-cdn.com/v4/letter/s/51bf81/32.png) [@suvarna](https://discuss.elastic.co/u/suvarna)\
**Post date:** [July 1, 2019, 3:37am UTC](https://discuss.elastic.co/t/elasticsearch-index-writes-is-really-do-flush-or-synch-at-os-level/188005/3 "2019-07-01T03:37:06Z")

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Hi,

Can you please elaborate your answer, whether index writer is really do flush() or synch() at OS level.

is it pure flush? happens at the time of index writer ..

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<div class="post-metadata">

**Author:** ![dadoonet](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dadoonet/32/137187_2.png) [@dadoonet](https://discuss.elastic.co/u/dadoonet)\
**Post date:** [July 1, 2019, 4:57am UTC](https://discuss.elastic.co/t/elasticsearch-index-writes-is-really-do-flush-or-synch-at-os-level/188005/4 "2019-07-01T04:57:38Z")

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I meant `fsync`.

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<div class="post-metadata">

**Author:** ![suvarna](https://avatars.discourse-cdn.com/v4/letter/s/51bf81/32.png) [@suvarna](https://discuss.elastic.co/u/suvarna)\
**Post date:** [July 5, 2019, 3:54am UTC](https://discuss.elastic.co/t/elasticsearch-index-writes-is-really-do-flush-or-synch-at-os-level/188005/5 "2019-07-05T03:54:31Z")

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Thanks

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [August 2, 2019, 3:54am UTC](https://discuss.elastic.co/t/elasticsearch-index-writes-is-really-do-flush-or-synch-at-os-level/188005/6 "2019-08-02T03:54:42Z")

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