# Confusion of elasticsearch

**URL:** <https://discuss.elastic.co/t/confusion-of-elasticsearch/56998>\
**Category:** Elasticsearch\
**Created:** [August 2, 2016, 11:32am UTC](https://discuss.elastic.co/t/confusion-of-elasticsearch/56998 "2016-08-02T11:32:09Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![ttjslbz](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@ttjslbz](https://discuss.elastic.co/u/ttjslbz)\
**Post date:** [August 2, 2016, 11:32am UTC](https://discuss.elastic.co/t/confusion-of-elasticsearch/56998/1 "2016-08-02T11:32:09Z")

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Hi , i am study the source of elk.  
As all know, there are two types of write operation in elasticseasrch , sync and unsync.  
I wonder. What does a sync operation really mean,  
If i write a document to primary and its replica in sync model, the writing operation on replica will return success signel on which point.  
The write operation record into translog ?  
or the translog flush to lucene index?

Looking forward your reply

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**Author:** ![cbuescher](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/cbuescher/32/60402_2.png) [@cbuescher](https://discuss.elastic.co/u/cbuescher)\
**Post date:** [August 3, 2016, 1:12pm UTC](https://discuss.elastic.co/t/confusion-of-elasticsearch/56998/2 "2016-08-03T13:12:11Z")

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Hi,

The ability to specify `async` replication for indexing operations is deprecated and removed in version 2.0.0 (see [https://github.com/elastic/elasticsearch/issues/10114](https://github.com/elastic/elasticsearch/issues/10114) for reference). Indexing operations with `sync` will return after they have been written to disk to the translog and are also written to the lucene in-memory buffer on primary and all replica shards. For reference: [https://www.elastic.co/guide/en/elasticsearch/guide/current/translog.html](https://www.elastic.co/guide/en/elasticsearch/guide/current/translog.html)

Cheers

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**Author:** ![ttjslbz](https://avatars.discourse-cdn.com/v4/letter/t/73ab20/32.png) [@ttjslbz](https://discuss.elastic.co/u/ttjslbz)\
**Post date:** [August 8, 2016, 8:58am UTC](https://discuss.elastic.co/t/confusion-of-elasticsearch/56998/3 "2016-08-08T08:58:29Z")

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Thanks, Christoph  
It helps me a lot to understand elk  
Thanks

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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, 10:29pm UTC](https://discuss.elastic.co/t/confusion-of-elasticsearch/56998/4 "2017-07-05T22:29:27Z")

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