cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Jeremiah Jordan <>
Subject Re: Cassandra in Multiple Datacenters Active - Standby configuration
Date Mon, 15 Aug 2011 21:35:18 GMT
Assign the tokens like they are two separate rings, just make sure you 
don't have any duplicate tokens.

The two datacenters are treated as separate rings, LOCAL_QUORUM will 
only delay the client as long as it takes to write the data to the local 
nodes.  The nodes in the other datacenter will get asynchronous writes.

On 08/15/2011 03:39 PM, Oleg Tsvinev wrote:
> Hi all,
> I have a question that documentation has not clear answer for. I have
> the following requirements:
> 1. Synchronously store data in datacenter DC1 on 2+ nodes
> 2. Asynchronously replicate the same data to DC2 and store it on 2+
> nodes to act as a hot standby
> Now, I have configured keyspaces with o.a.c.l.NetworkTopologyStrategy
> with strategy_options=[{DC1:2, DC2:2}] and use LOCAL_QUORUM
> consistency level, following documentation here:
> Now, how do I assign initial tokens? If I have, say 6 nodes total, 3
> in DC1 and 3 in DC2, and create a ring as if all 6 nodes share the
> total 2^128 space equally.
> Now say node N1:DC2 has key K and is in remote datacenter (for an app
> in DC1). Wouldn't Cassandra always forward K to the DC2 node N1 thus
> turning asynchronous writes into synchronous ones? Performance impact
> will be huge as the latency between DC1 and DC2 is significant.
> I hope there's an answer and I'm just missing something. My case falls
> under Disaster Recovery in
> but I don't see
> how Cassandra will support my use case.
> I appreciate any help on this.
> Thank you,
>    Oleg

View raw message