# Reindex API is extremely slow **URL:** \ **Category:** Elasticsearch\ **Tags:** reindex\ **Created:** [May 20, 2021, 10:51am UTC](https://discuss.elastic.co/t/reindex-api-is-extremely-slow/273510 "2021-05-20T10:51:41Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![abhinav2](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/abhinav2/32/46615_2.png) [@abhinav2](https://discuss.elastic.co/u/abhinav2)\ **Post date:** [May 20, 2021, 10:51am UTC](https://discuss.elastic.co/t/reindex-api-is-extremely-slow/273510/1 "2021-05-20T10:51:41Z")
I'm getting a write speed of 680 KB/s per node for the reindex API. Cluster is a 16 data node cluster with 3 master nodes. Each data node has 1.3 TB gp3 Disk with 3000 IOPS and 125 MBps throughput. Reindex API is using a batch of 6176 documents (~ 3MB payload size) Why is it so slow? ---
**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:** [May 27, 2021, 6:57am UTC](https://discuss.elastic.co/t/reindex-api-is-extremely-slow/273510/2 "2021-05-27T06:57:26Z")
Which version of Elasticsearch are you using? How large is the index you are reindexing? How many primary and replica shards does it have? How are you running the reindex operation? Have you tried [slicing](https://www.elastic.co/guide/en/elasticsearch/reference/7.13/docs-reindex.html#docs-reindex-slice) to improve concurrency? Have you tried with different bulk sizes? ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [June 24, 2021, 6:57am UTC](https://discuss.elastic.co/t/reindex-api-is-extremely-slow/273510/3 "2021-06-24T06:57:42Z")
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