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From Sameer Farooqui <>
Subject Re: question on setup for writes into 2 datacenters
Date Fri, 22 Jul 2011 22:04:46 GMT
It sounds like what you're looking for is write consistency of local_quorum:

local_quorum would mean the write has to be successful on a majority of
nodes in DC1 (so 2) before it is considered successful.

If you use just quorum write, it'll have to be committed to 3 replicas out
of the 4 before it's considered successful.

On Fri, Jul 22, 2011 at 1:57 PM, Dean Hiller <> wrote:

> Ideally, we would want to have a replication factor of 4, and a minimum
> write consistency of 2 (which looking at the default in cassandra.yaml is to
> memory first with asynch to disk...perfect so far!!!)
> Now, obviously, I can get the partitioner setup to make sure I get 2
> replicas in each data center.  The next thing I would want to guarantee
> however is that if a write came into datacenter 1, it would write to the two
> nodes in datacenter 1 and asynchronously replicate to datacenter 2.  Is this
> possible?  Does cassandra already handle that or is there something I could
> do to get cassandra to do that?
> In this mode, I believe I can have both datacenters be live as well as be
> backup for the other not wasting resources.
> thanks,
> Dean

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