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From Edward Capriolo <edlinuxg...@gmail.com>
Subject Re: Multi Data Center Strategy
Date Mon, 11 Oct 2010 15:26:38 GMT
On Mon, Oct 11, 2010 at 9:53 AM, Henry Luo <hluo@choicestream.com> wrote:
> We have an application that does a lot of updates to the rows. We use
> replication factor of 3 and are moving to multiple data centers. We would
> like to accomplish the following setup:
>
>
>
> Data are replicated to other data centers. RackAwareStrategy seems to be
> able to handle that, however
>
>
>
> 1)      We don’t need the data replicated across data centers for each
> individual update, since they got overridden a lot. Rather, we’d like it be
> replicated ‘once a while’, say after x number of updates to a row, or after
> y number of minutes. In essence, it’s a delayed write of the latest copy
> only to remote nodes.
>
> 2)      We would like the read be handled only by the nodes local to the
> client, i.e., don’t bother to send read requests to the remote data center
> since it’s too slow. If the request fails locally, just let it fail.
>
>
>
> Is there a way to accomplish this by
>
> 1)      Configure Cassandra in a certain way
>
> 2)      Change/Add replication strategy
>
> 3)      Change/Add some core Cassandra features
>
> 4)      Use another layer in front of Cassandra – I’d rather not to go this
> route.
>
>
>
> Thanks.
>
>
>
> Henry
>
>
>
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1) No you can not do this. In 7.0 you can set the read_repair_chance
to a low % so read repairs only happen periodically.

2) If you have your multi-data center configuration setup properly
with respect to snitches, and you read at Consistency Level ONE, or
DCQuorum, and set read_repair_chance to a low % as specified above you
will achieve this.

Edward

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