# Rack awareness in Elastic Search **URL:** \ **Category:** Elasticsearch\ **Created:** [July 18, 2011, 3:17pm UTC](https://discuss.elastic.co/t/rack-awareness-in-elastic-search/4884 "2011-07-18T15:17:15Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Eran\_Kutner](https://avatars.discourse-cdn.com/v4/letter/e/e9c0ed/32.png) [@Eran\_Kutner](https://discuss.elastic.co/u/Eran_Kutner)\ **Post date:** [July 18, 2011, 3:17pm UTC](https://discuss.elastic.co/t/rack-awareness-in-elastic-search/4884/1 "2011-07-18T15:17:15Z")
Hi, As mentioned in my previous post there are a few critical missing features in Elastic Search I'd like to address. The second one, is what is known in Hadoop and Cassandra as "Rack awareness". Basically it is the ability to group nodes into distinct groups which are supposed to be physically redundant and have to system consider this when allocating shards. For example let's say we have 5 physical servers connected to UPS A and another 5 connected to UPS B. If one of the UPSs fails it will take down all the servers connected to it but the other 5 servers will continue running as usual. If we have 1 replica for each shard, theoretically the system should be OK and continue to operate normally under the above situation, but for this to happen we need to guarantee that the two replicas of a shard are never hosted on servers connected to the same UPS. If there was a way to assign each server to a named group such as "UPS\_A" and "UPS\_B" and make sure the shard replication process always preferred to distribute replicas on as many groups as possible that would give the desired behavior. Again, would appreciate any feedback. -eran ---
**Author:** ![kimchy](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/kimchy/32/44952_2.png) [@kimchy](https://discuss.elastic.co/u/kimchy)\ **Post date:** [July 18, 2011, 5:33pm UTC](https://discuss.elastic.co/t/rack-awareness-in-elastic-search/4884/2 "2011-07-18T17:33:29Z")
Yea, this is not implemented yet but high on the road map. On Mon, Jul 18, 2011 at 6:17 PM, Eran Kutner [eran@gigya.com](mailto:eran@gigya.com) wrote: > Hi, > As mentioned in my previous post there are a few critical missing > features in Elastic Search I'd like to address. > The second one, is what is known in Hadoop and Cassandra as "Rack > awareness". Basically it is the ability to group nodes into distinct > groups which are supposed to be physically redundant and have to > system consider this when allocating shards. > For example let's say we have 5 physical servers connected to UPS A > and another 5 connected to UPS B. If one of the UPSs fails it will > take down all the servers connected to it but the other 5 servers will > continue running as usual. If we have 1 replica for each shard, > theoretically the system should be OK and continue to operate normally > under the above situation, but for this to happen we need to guarantee > that the two replicas of a shard are never hosted on servers connected > to the same UPS. > If there was a way to assign each server to a named group such as > "UPS\_A" and "UPS\_B" and make sure the shard replication process always > preferred to distribute replicas on as many groups as possible that > would give the desired behavior. > > Again, would appreciate any feedback. > > -eran ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [July 6, 2017, 4:00am UTC](https://discuss.elastic.co/t/rack-awareness-in-elastic-search/4884/3 "2017-07-06T04:00:15Z")
Closed on July 6, 2017, 4:00am UTC