# Understanding Aliases
**URL:** https://discuss.elastic.co/t/understanding-aliases/152255
**Category:** Elasticsearch
**Created:** [October 12, 2018, 2:06pm UTC](https://discuss.elastic.co/t/understanding-aliases/152255 "2018-10-12T14:06:07Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@jlixfeld](https://discuss.elastic.co/u/jlixfeld)
#### Post date: [October 12, 2018, 2:06pm UTC](https://discuss.elastic.co/t/understanding-aliases/152255/1 "2018-10-12T14:06:07Z")
Hi!
I have an application that is talking to an index which I need to re-index with an additional shard. I understand that aliasing can help here, but I'm fuzzy on some stuff...
The index name is `elastiflow-3.3.0-2018.10.06`
Based on my understanding of [Index Aliases](https://www.elastic.co/guide/en/elasticsearch/reference/current/indices-aliases.html#indices-aliases), if I create an alias called `elastiflow-3.3.0-2018.10.06-v1`, it's going to do stuff in the backend to make any applications that used to talk to `elastiflow-3.3.0-2018.10.06` now talk to `elastiflow-3.3.0-2018.10.06-v1` instead.
At that point, [Index Aliases and Zero Downtime](https://www.elastic.co/guide/en/elasticsearch/guide/master/index-aliases.html) suggests that I create the new index (which would include the appropriate settings for the additional shard) and then proceed to re-index `elastiflow-3.3.0-2018.10.06-v1` to `elastiflow-3.3.0-2018.10.06-v2`. That part is fuzzy to me. Wouldn't I be better off to re-index `elastiflow-3.3.0-2018.10.06` to `elastiflow-3.3.0-2018.10.06-v2`?
Once the re-indexing is done, I'm supposed to change the alias for `elastiflow-3.3.0-2018.10.06` to point to `elastiflow-3.3.0-2018.10.06-v2` now. The question at this point, is I think I now have 20GB of disk space that has been duplicated due to the reindexing of `elastiflow-3.3.0-2018.10.06-v1` to `elastiflow-3.3.0-2018.10.06-v2`, but `elastiflow-3.3.0-2018.10.06-v1` is an alias, so technically it's empty and a pointer to `elastiflow-3.3.0-2018.10.06`, which actually has all the original data. But, if I delete `elastiflow-3.3.0-2018.10.06`, don't I break the `elastiflow-3.3.0-2018.10.06-v2` alias since it's an alias for `elastiflow-3.3.0-2018.10.06` or does the alias voodoo take care of any references to the old index name, such that it is, in some way detached from the application so it can be deleted?
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [November 9, 2018, 2:06pm UTC](https://discuss.elastic.co/t/understanding-aliases/152255/2 "2018-11-09T14:06:08Z")
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