# Elasticsearch replica shard distribution **URL:** \ **Category:** Elasticsearch\ **Created:** [August 1, 2017, 3:12pm UTC](https://discuss.elastic.co/t/elasticsearch-replica-shard-distribution/95371 "2017-08-01T15:12:04Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![monkegoist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/monkegoist/32/20684_2.png) [@monkegoist](https://discuss.elastic.co/u/monkegoist)\ **Post date:** [August 1, 2017, 3:12pm UTC](https://discuss.elastic.co/t/elasticsearch-replica-shard-distribution/95371/1 "2017-08-01T15:12:05Z")
Hello, We recently came across an issue with users reporting their queries being slow. There are 5 nodes in a cluster, index has 10 shards, replication factor is 1. Upon investigation, I found out that each of the nodes has 4 shards allocated to it, but for one node all of the shards are replicas while others contain only 1 or 2 replica shards. As far as I understand, search queries are executed against replica shards which would explain why this node suffers the most (judging by slow queries log and kopf cluster health info). Is there a way to adjust cluster settings in such a way that both primary and replica shards are allocated evenly? Or is there another approach that we could use in our case? Thanks in advance for your help! ---
**Author:** ![leandrojmp](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/leandrojmp/32/107231_2.png) [@leandrojmp](https://discuss.elastic.co/u/leandrojmp)\ **Post date:** [August 1, 2017, 3:40pm UTC](https://discuss.elastic.co/t/elasticsearch-replica-shard-distribution/95371/2 "2017-08-01T15:40:00Z")
> [@monkegoist](#): > > As far as I understand, search queries are executed against replica shards which would explain why this node suffers the most (judging by slow queries log and kopf cluster health info). I think that is not true, according to the documentation, [replicas and primaries do the same amount of work](https://www.elastic.co/guide/en/elasticsearch/guide/master/replica-shards.html#img-three-nodes). The cause of the slow queries must be something else. It is only one node that shows performance issue? ---
**Author:** ![monkegoist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/monkegoist/32/20684_2.png) [@monkegoist](https://discuss.elastic.co/u/monkegoist)\ **Post date:** [August 3, 2017, 2:33pm UTC](https://discuss.elastic.co/t/elasticsearch-replica-shard-distribution/95371/3 "2017-08-03T14:33:35Z")
Hi Leandro, You're right, my statement about query execution against replica shards seems to be false. I checked Elastic source code and found out that if preference isn't specified, random order seems to be used (`IndexShardRoutingTable#activeInitializingShardsRandomIt()`). Here's what I have in slow logs for the query in question: node 1: ``` [2017-08-01 14:01:06,286][WARN][index.search.slowlog.query] [Snowfall] [index][0] took[5.2s], took_millis[5242] - primary [2017-08-01 14:01:07,351][WARN][index.search.slowlog.query] [Snowfall] [index][2] took[6.2s], took_millis[6293] - primary [2017-08-01 14:01:07,374][WARN][index.search.slowlog.query] [Snowfall] [index][1] took[6s], took_millis[6085] - primary ``` node 2: ``` [2017-08-01 14:02:23,111][WARN][index.search.slowlog.query] [Luchino Nefaria] [index][7] took[43.2s], took_millis[43201] - replica [2017-08-01 14:02:49,445][WARN][index.search.slowlog.query] [Luchino Nefaria] [index][9] took[1.7m], took_millis[106090] - replica [2017-08-01 14:02:54,152][WARN][index.search.slowlog.query] [Luchino Nefaria] [index][3] took[1.8m], took_millis[113128] - replica [2017-08-01 14:03:27,645][WARN][index.search.slowlog.query] [Luchino Nefaria] [index][5] took[2.4m], took_millis[144610] - replica ``` node 3: nothing node 4: ``` [2017-08-01 14:01:17,866][WARN][index.search.slowlog.query] [Xemnu the Titan] [index][4] took[16.7s], took_millis[16747] - primary [2017-08-01 14:01:21,942][WARN][index.search.slowlog.query] [Xemnu the Titan] [index][6] took[20.8s], took_millis[20837] - primary ``` node 5: `[2017-08-01 14:01:05,856][WARN][index.search.slowlog.query] [Gideon] [index][8] took[4.8s], took_millis[4815] - replica` As you can see, node 2 had the most work to do. Although node 1 had a lot of work too but managed to complete it much faster. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [August 31, 2017, 2:34pm UTC](https://discuss.elastic.co/t/elasticsearch-replica-shard-distribution/95371/4 "2017-08-31T14:34:07Z")
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