Reduce number of shards in ElasticSearch

Question

Is it possible to reduce the number of shards in ElasticSearch search engine once the index is created ?

I tried :

$ curl -XPUT 'localhost:9200/myindex/_settings' -d '{"index" : {"number_of_shards" : 3}}'

But it gives an error :

{"error":"ElasticsearchIllegalArgumentException[can't change the number of shards for an index]","status":400}

Answer 1

This is no longer true, with 5.x you can shring the number of indexes to a whole fraction. For example from 12 you could go down to 1, 2, 3 or 6 (see the docs). But you must put it to read-only mode and naturally the shrinking process requires lots of IO.

Answer 2

No, it's not possible. You could change a lot of stuff - e.g. number of replicas for each shard, or many other index settings, but not the number of shards.

For more information - take a look here - http://www.elastic.co/guide/en/elasticsearch/reference/1.5/indices-update-settings.html