# Reindex API - Need to improve performance
**URL:** https://discuss.elastic.co/t/reindex-api-need-to-improve-performance/285453
**Category:** Elasticsearch
**Tags:** reindex
**Created:** [September 29, 2021, 9:06am UTC](https://discuss.elastic.co/t/reindex-api-need-to-improve-performance/285453 "2021-09-29T09:06:19Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Seba](https://discuss.elastic.co/u/Seba)
#### Post date: [September 29, 2021, 9:06am UTC](https://discuss.elastic.co/t/reindex-api-need-to-improve-performance/285453/1 "2021-09-29T09:06:19Z")
Hello,
The goal is to accelerate the reindex of indexes from an ELK cluster (version 7.6.2) composed of 3 nodes each with all the roles to a datastream in an ELK cluster (version 7.11) installed in a container system with a total of 11 nodes: 2 coordinators, 3 masters, 3 data\_hot node, 3 noed data\_warm
Some information about the indexes to be transferred: 189 indexes with 1 replica, a little bit more than 5 TB of data, 6 532 237 567 docs.
With the reindex function, I have already done several tests (changing the refresh interval, with / without replica, several reindexes in parallel to the same datastream, ...) and it works correctly but it takes time!
Concretely to reindex 1 index of 30 Gb, 34 731 806 docs to a datastream without replica and with a refresh\_interval equal to 300s it takes about 12h to realize the transfer.
I am looking for ideas to improve the performance of this transfer.
Thanks in advance, 😉
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### Author:  [@warkolm](https://discuss.elastic.co/u/warkolm)
#### Post date: [September 29, 2021, 10:26pm UTC](https://discuss.elastic.co/t/reindex-api-need-to-improve-performance/285453/2 "2021-09-29T22:26:54Z")
Welcome to our community! 😃
If you've done all of that so far and are unable to improve speeds, can you increase the size of your cluster?
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### Author:  [@Seba](https://discuss.elastic.co/u/Seba)
#### Post date: [October 4, 2021, 9:40am UTC](https://discuss.elastic.co/t/reindex-api-need-to-improve-performance/285453/3 "2021-10-04T09:40:07Z")
Hello,
Yes, I can increase the size of the cluster if really necessary, but since it's production, it has to be justified... 😉
In addition, I forgot to mention this, but I need to re-index into an existing datastream that already contains production data. So I have to be careful what I do.
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [November 1, 2021, 9:40am UTC](https://discuss.elastic.co/t/reindex-api-need-to-improve-performance/285453/4 "2021-11-01T09:40:14Z")
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