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From Richard Low <rich...@wentnet.com>
Subject Re: How many seed nodes should I use?
Date Thu, 29 Aug 2013 15:04:53 GMT
On 29 August 2013 01:55, Ike Walker <ike.walker@flite.com> wrote:

> What is the best practice for how many seed nodes to have in a Cassandra
> cluster? I remember reading a recommendation of 2 seeds per datacenter in
> Datastax documentation for 0.7, but I'm interested to know what other
> people are doing these days, especially in AWS.
>
> I'm running a cluster of 12 nodes at AWS. Each node runs Cassandra 1.2.5
> on an m1.xlarge EC2 instance, and they are spread across 3 availability
> zones within a single region.
>
> To keep things simple I currently have all 12 nodes listed as seeds. That
> seems like overkill to me, but I don't know the pros and cons of too many
> or too few seeds.
>

Seeds are used for bootstrapping a new node so it can discover the others.
 Existing nodes store a list of the other nodes it has seen so doesn't need
the seeds each time it starts up.  Seeds are treated slightly differently
in gossip though to ensure a node keeps trying to connect to seeds in case
of a partition.

The best recommendations are to use the same seed list on each node and
just a few.  More than your replication factor is almost certainly too
many, but the cost of too many is very little.

Richard.

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