# Does \_split actually splits data or just copies it across shards
**URL:** https://discuss.elastic.co/t/does-split-actually-splits-data-or-just-copies-it-across-shards/315164
**Category:** Elasticsearch
**Created:** [September 26, 2022, 11:26am UTC](https://discuss.elastic.co/t/does-split-actually-splits-data-or-just-copies-it-across-shards/315164 "2022-09-26T11:26:12Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@danskiyq](https://discuss.elastic.co/u/danskiyq)
#### Post date: [September 26, 2022, 11:26am UTC](https://discuss.elastic.co/t/does-split-actually-splits-data-or-just-copies-it-across-shards/315164/1 "2022-09-26T11:26:12Z")
I want to create a new index with bigger amount of shards and copy my data across. \_reindex would probably be the best solution, but I expected split to do what I wanted.
So I have 38gb 1shard index and I wanted to split it into 4 shards index. I expected new index to have same amount of store.size and 4 shards, but instead store.size of a new index turned out to be 97gb, what's the reason behind it and how \_split actually works.
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### Author:  [@carly.richmond](https://discuss.elastic.co/u/carly.richmond)
#### Post date: [September 26, 2022, 12:02pm UTC](https://discuss.elastic.co/t/does-split-actually-splits-data-or-just-copies-it-across-shards/315164/2 "2022-09-26T12:02:31Z")
Hi Danyil,
The number of splits is determined by the index setting `index.number_of_routing_shards`. The docs entry [here](https://www.elastic.co/guide/en/elasticsearch/reference/8.4/indices-split-index.html#split-index-api-desc) include more details and examples that should help explain how splitting works.
Hope that helps.
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### Author:  [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)
#### Post date: [September 26, 2022, 12:04pm UTC](https://discuss.elastic.co/t/does-split-actually-splits-data-or-just-copies-it-across-shards/315164/3 "2022-09-26T12:04:55Z")
I would recommend looking at the discusion in this [recent thread](https://discuss.elastic.co/t/how-does-elasticsearch-splitting-an-index-work/313319).
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### Author:  [@danskiyq](https://discuss.elastic.co/u/danskiyq)
#### Post date: [September 26, 2022, 3:24pm UTC](https://discuss.elastic.co/t/does-split-actually-splits-data-or-just-copies-it-across-shards/315164/5 "2022-09-26T15:24:53Z")
I understand the concept, but it's still confusing to me.
In a nutshell, if I split 1shard index into 4 shards index, does it split that shard's data or instead copies it across all those newly created shards?
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### Author:  [@carly.richmond](https://discuss.elastic.co/u/carly.richmond)
#### Post date: [September 26, 2022, 3:50pm UTC](https://discuss.elastic.co/t/does-split-actually-splits-data-or-just-copies-it-across-shards/315164/6 "2022-09-26T15:50:13Z")
[Looking at this answer in another thread](https://discuss.elastic.co/t/cloned-split-indexes-take-double-disk-space-when-increasing-shards/254342/4), which is referenced in the discussion posted by @Christian_Dahlqvist, the shards are cloned and then docs are deleted in a similar way to delete by query.
The thread referenced above does walk through an example which may help explain further.
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [October 24, 2022, 3:50pm UTC](https://discuss.elastic.co/t/does-split-actually-splits-data-or-just-copies-it-across-shards/315164/7 "2022-10-24T15:50:58Z")
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