# Architecture

**URL:** <https://discuss.elastic.co/t/architecture/5051>\
**Category:** Elasticsearch\
**Created:** [August 4, 2011, 1:38am UTC](https://discuss.elastic.co/t/architecture/5051 "2011-08-04T01:38:24Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jjasinek](https://avatars.discourse-cdn.com/v4/letter/j/b782af/32.png) [@jjasinek](https://discuss.elastic.co/u/jjasinek)\
**Post date:** [August 4, 2011, 1:38am UTC](https://discuss.elastic.co/t/architecture/5051/1 "2011-08-04T01:38:24Z")

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I've been doing research against various distributed search systems as  
well as "NoSQL" K/V storage systems and have come to look into  
utilizing ElasticSearch for our searching (and possibly for our K/V as  
well). However, I have a few questions regarding it's durability and  
distributed nature since I can't seem to find much information online  
about this.

I've seen mention of a "master node" that maintains global state and  
reassigns shards. How does the system react if the "master"  
partitions from the cluster for any reason (network partition, hdd  
crash, etc)? Does another node self-promote? What happens when this  
"master" comes back online?

I've also seen that shards and backups are utlized in ElasticSearch  
instead of a "ring" as defined in the Dynamo paper. This sounds  
similar to other distributed databases such as MongoDB (shards,  
replica sets, and replicas) but I can't seem to find any information  
about this. Is there somewhere online that I can review the sharding  
and replica information? I reviewed  
[http://www.elasticsearch.org/blog/2010/02/16/searchengine\_time\_machine.html](http://www.elasticsearch.org/blog/2010/02/16/searchengine_time_machine.html)  
but it doesn't quite explain everything. I'm looking to see how an  
index is broken into shards, what happens when shard replicas are  
partitioned from the group at the time of a write (do they "sync" up  
when they come back online), and even how the long term peristency  
with the local gateway storage, and what happens when we crash before  
information is written to this long term storage?

Any information is appreciated,  
Jason

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**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, 3:58am UTC](https://discuss.elastic.co/t/architecture/5051/2 "2017-07-06T03:58:19Z")

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Closed on July 6, 2017, 3:58am UTC