# How to migrate index A to index B in Elasticsearch without stopping writes to index A?
**URL:** https://discuss.elastic.co/t/how-to-migrate-index-a-to-index-b-in-elasticsearch-without-stopping-writes-to-index-a/372198
**Category:** Elastic Search
**Tags:** reindex
**Created:** [December 19, 2024, 5:40am UTC](https://discuss.elastic.co/t/how-to-migrate-index-a-to-index-b-in-elasticsearch-without-stopping-writes-to-index-a/372198 "2024-12-19T05:40:39Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@WangXiang727](https://discuss.elastic.co/u/WangXiang727)
#### Post date: [December 19, 2024, 5:40am UTC](https://discuss.elastic.co/t/how-to-migrate-index-a-to-index-b-in-elasticsearch-without-stopping-writes-to-index-a/372198/1 "2024-12-19T05:40:39Z")
I'm using Elasticsearch 7.10.0 and need to migrate data from index A to a new index B without interrupting write operations to index A. I want to achieve zero downtime during this migration and to migrate both the existing (historical) data and the new, incoming (incremental) data.
Here's my current situation:
- **Elasticsearch Version:** 7.10.0
- **Source Index:** A (actively receiving writes)
- **Destination Index:** B (newly created, needs to be populated with data from A)
- **Constraint:** I've found that using the Reindex API in my 7.10.0 setup can lead to significant performance degradation on index A or even data inconsistency issues. Therefore, I'm looking for alternative solutions that avoid or minimize the use of Reindex for bulk data transfer.
- **Requirement:** Migrate both the full historical data from A and ensure that all new data written to A after the initial migration starts is also continuously synced to B.
Any advice, examples, or pointers to relevant documentation would be greatly appreciated. Thanks in advance for your help!
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### Author:  [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)
#### Post date: [December 19, 2024, 6:33am UTC](https://discuss.elastic.co/t/how-to-migrate-index-a-to-index-b-in-elasticsearch-without-stopping-writes-to-index-a/372198/2 "2024-12-19T06:33:06Z")
> [@WangXiang727](#):
>
> I'm using Elasticsearch 7.10.0
This is really old and have been EOL and without security updates for a long time. I recommend that you upgrade to the latest version of Elasticsearch.
Are you just adding new data or also performing updates and/or deletes?
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### Author:  [@WangXiang727](https://discuss.elastic.co/u/WangXiang727)
#### Post date: [December 19, 2024, 7:06am UTC](https://discuss.elastic.co/t/how-to-migrate-index-a-to-index-b-in-elasticsearch-without-stopping-writes-to-index-a/372198/3 "2024-12-19T07:06:19Z")
I get it, this version is super old , but we’re stuck with it for now because of some external reasons. My data is just write-only though—no updates or deletes.
Any idea how I can fix this? Would really appreciate you help!
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### Author:  [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)
#### Post date: [December 19, 2024, 7:21am UTC](https://discuss.elastic.co/t/how-to-migrate-index-a-to-index-b-in-elasticsearch-without-stopping-writes-to-index-a/372198/4 "2024-12-19T07:21:42Z")
> [@WangXiang727](#):
>
> My data is just write-only though—no updates or deletes.
That makes it a lot easier. As you will need to reindex all the data there will be additional load and there is no way to avoid that. I would probebly try creating the new index and then redirecting new writes there. Once the old index is no longer written to you can start a reindexing job of this data to the new index. You will have duplicates for a period of time if both indices are included in queries, but this will go away once reindexing is done and the old index is deleted.
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### Author:  [@WangXiang727](https://discuss.elastic.co/u/WangXiang727)
#### Post date: [December 19, 2024, 7:38am UTC](https://discuss.elastic.co/t/how-to-migrate-index-a-to-index-b-in-elasticsearch-without-stopping-writes-to-index-a/372198/5 "2024-12-19T07:38:07Z")
Thank you this is very helpful to me.
I will design a technical solution based on your ideas (ﾉ\>ω\<)ﾉ
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [January 16, 2025, 7:38am UTC](https://discuss.elastic.co/t/how-to-migrate-index-a-to-index-b-in-elasticsearch-without-stopping-writes-to-index-a/372198/6 "2025-01-16T07:38:16Z")
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