# Reindex performence
**URL:** https://discuss.elastic.co/t/reindex-performence/43846
**Category:** Elasticsearch
**Created:** [March 9, 2016, 1:56am UTC](https://discuss.elastic.co/t/reindex-performence/43846 "2016-03-09T01:56:51Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@lizhenmxcz](https://discuss.elastic.co/u/lizhenmxcz)
#### Post date: [March 9, 2016, 1:56am UTC](https://discuss.elastic.co/t/reindex-performence/43846/1 "2016-03-09T01:56:51Z")
hi, I changed the index mapping and need to reindex. There are about 7 billion records and 2T in disk. I try to use the elasticdump, but it is too slowly. Can i copy the old index data to the corresponding directory of new index ? or any other way to obtain the best performance
---
### Author:  [@nik9000](https://discuss.elastic.co/u/nik9000)
#### Post date: [March 9, 2016, 2:10am UTC](https://discuss.elastic.co/t/reindex-performence/43846/2 "2016-03-09T02:10:19Z")
The whole point of reindexing after the mapping is that the index needs to be rebuilt. So it isn't possible to copy files, no. Your options are just the normal ones for increasing index speed: make sure you are using \_bulk, raise the refresh interval, etc.
---
### Author:  [@lizhenmxcz](https://discuss.elastic.co/u/lizhenmxcz)
#### Post date: [March 9, 2016, 2:25am UTC](https://discuss.elastic.co/t/reindex-performence/43846/3 "2016-03-09T02:25:27Z")
thanks to @nik9000, I got it. I need to index it one by one . Can you give me some advice about the tools like elasticdump? I copy document in same cluster, and which tools can get best index speed in the situation
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 5, 2017, 11:10pm UTC](https://discuss.elastic.co/t/reindex-performence/43846/4 "2017-07-05T23:10:04Z")