# Multi-availability-zones HA cluster on AWS EC2 instances **URL:** \ **Category:** Elasticsearch\ **Created:** [October 24, 2019, 10:51pm UTC](https://discuss.elastic.co/t/multi-availability-zones-ha-cluster-on-aws-ec2-instances/205164 "2019-10-24T22:51:46Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![ffknob](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/ffknob/32/37008_2.png) [@ffknob](https://discuss.elastic.co/u/ffknob)\ **Post date:** [October 24, 2019, 10:51pm UTC](https://discuss.elastic.co/t/multi-availability-zones-ha-cluster-on-aws-ec2-instances/205164/1 "2019-10-24T22:51:46Z")
Hello... I am more of a developer than ops, so I am wondering how to deploy a HA cluster on AWS' EC2 instances. The thing is, I want this cluster to survive a zone failure... Here's what I have planned so far: - 7.4.0 - Across 2 availability zones (say, A and B) - Each node will be properly configured with an attribute that indicates to which zone it belongs - Cluster and indices will be aware of that, so it can allocate replicas to the other zone - I was thinking of having 3-node in each zone, so if one zone completly fails, the election between the three remaining node is successeful - Each node will act as master eligible and data The questions I have now: - Do we still have to have at least 3 node to avoid split brain? (I didn't kept up to date with some change in \> 7 that I think solved that) - In this scenario the total 6 node must be working all the time. Is there a more cost effective way to assure the HA cross availability zones? - How should I set the network configuration for the discoery phase? Install and use the EC2 plugin? - And what about the clients? How should they be configured to access this cluster in a HA fashion? Should I list all the nodes IPs in the "hosts" attribute, so in case of a failure it trys the next one? - Or should I have some balancer in front of the cluster? I'll appreciate any info you can give me. If there's already a post, an Elastic's blog or an article giving guidelines around this scenario, please send them my way. As I said, I more used to writinf queries than to deploying clusters... Thank you! ---
**Author:** ![inhinyera16](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/inhinyera16/32/61625_2.png) [@inhinyera16](https://discuss.elastic.co/u/inhinyera16)\ **Post date:** [October 25, 2019, 3:40am UTC](https://discuss.elastic.co/t/multi-availability-zones-ha-cluster-on-aws-ec2-instances/205164/2 "2019-10-25T03:40:30Z")
Try HA Proxy with load balancing in Layer 7, you can check here.. > **[How To Set Up Highly Available HAProxy Servers with Keepalived and Floating...](https://www.digitalocean.com/community/tutorials/how-to-set-up-highly-available-haproxy-servers-with-keepalived-and-floating-ips-on-ubuntu-14-04)** > > High availability is a function of system design that allows an application to automatically restart or reroute work to another capable system in the event of a failure. In terms of servers, there are a few different technologies needed to set up a... ---
**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\ **Post date:** [October 25, 2019, 5:07am UTC](https://discuss.elastic.co/t/multi-availability-zones-ha-cluster-on-aws-ec2-instances/205164/3 "2019-10-25T05:07:42Z")
In order to make your cluster highly available I case of AZ failure you need to deploy the cluster across 3AZ so that a strict majority of master eligible nodes will survive the crash. ---
**Author:** ![ffknob](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/ffknob/32/37008_2.png) [@ffknob](https://discuss.elastic.co/u/ffknob)\ **Post date:** [October 25, 2019, 12:34pm UTC](https://discuss.elastic.co/t/multi-availability-zones-ha-cluster-on-aws-ec2-instances/205164/4 "2019-10-25T12:34:36Z")
Hello @Christian_Dahlqvist I am curious about the need for 3 AZs. When it comes to be protected from the failure of one AZ my reasoning is: - A minimal production cluster formation needs 3 master eligible nodes to have a successeful voting process - In the event of a AZ failure, I'd need other 3 master eligible nodes in the remaining zone in order to a new master to assume - Other than that I would need all these 3 nodes (which will also be data nodes) to have the necessary primary and replica shards to assure green state So the way I see, I would need 6 nodes, 3 in each zone, so that if I completly lose a zone, the other one has everything it needs to assume. In a health zone state I would have a 6 node cluster, which would probably help to improve performance, but seens totaly unecessary and expensive to my use case... Am I missing something? Do you guys know some article that gives guidelines for deploying a cluster in a multi-zone architecture? By the way, thanks for having interest and taking the time to answer my question. ---
**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\ **Post date:** [October 25, 2019, 2:07pm UTC](https://discuss.elastic.co/t/multi-availability-zones-ha-cluster-on-aws-ec2-instances/205164/5 "2019-10-25T14:07:29Z")
All nodes across both AZ form a single cluster. In any failure scenario you need a strict majority of master eligible nodes to still be available in order to have a healthy and functioning cluster. If you have 6 nodes a minimum of 4 (majority of 6) nodes which does not allow a full AZ to go down. If you however have at least one master eligible node in a third AZ you get around this as the majority of 7 is still 4. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [November 22, 2019, 2:07pm UTC](https://discuss.elastic.co/t/multi-availability-zones-ha-cluster-on-aws-ec2-instances/205164/6 "2019-11-22T14:07:31Z")
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