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From Sylvain Lebresne <sylv...@datastax.com>
Subject Re: Consistency level for multi-datacenter setup
Date Mon, 03 Jun 2013 20:36:39 GMT
What's your replication factor? Do you have RF=2 on both datacenters?


On Mon, Jun 3, 2013 at 10:09 PM, srmore <comomore@gmail.com> wrote:

> I am a bit confused when using the consistency level for multi datacenter
> setup. Following is my setup:
>
> I have 4 nodes the way these are set up are
> Node 1 DC 1 - N1DC1
> Node 2 DC 1 - N2DC1
>
> Node 1 DC 2 - N1DC2
> Node 2 DC 2 - N2DC2
>
> I setup a delay in between two datacenters (DC1 and DC2 around 1 sec one
> way)
>
> I am observing that when I use consistency level 2 for some reason the
> coordinate node is picking up the nodes from other datacenter. My
> understanding was that Cassandra picks up nodes which are close by (from
> local datacenter), determined by Gossip but looks like that's not the case.
>
> I found the following comment on Datastax website :
>
> "If using a consistency level of ONE or LOCAL_QUORUM, only the nodes in
> the same data center as the coordinator node must respond to the client
> request in order for the request to succeed."
>
> Does this mean that for multi datacenter we can only use ONE or
> LOCAL_QUORUM if we want to use the local datacenter to avoid cross
> datacenter latency.
>
> I am using the GossipingPropertyFileSnitch.
>
> Thanks !
>
>

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