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Date: Mon, 11 Oct 2010 11:26:38 -0400
Message-ID: <AANLkTi=KzK9GdFkYGhzuo_SSfh_Z83p22D-8vGpdi0JM@mail.gmail.com>
Subject: Re: Multi Data Center Strategy
From: Edward Capriolo <edlinuxguru@gmail.com>
To: user@cassandra.apache.org
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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)=A0=A0=A0=A0=A0 We don=92t need the data replicated across data centers=
 for each
> individual update, since they got overridden a lot. Rather, we=92d like i=
t be
> replicated =91once a while=92, say after x number of updates to a row, or=
 after
> y number of minutes. In essence, it=92s a delayed write of the latest cop=
y
> only to remote nodes.
>
> 2)=A0=A0=A0=A0=A0 We would like the read be handled only by the nodes loc=
al to the
> client, i.e., don=92t bother to send read requests to the remote data cen=
ter
> since it=92s too slow. If the request fails locally, just let it fail.
>
>
>
> Is there a way to accomplish this by
>
> 1)=A0=A0=A0=A0=A0 Configure Cassandra in a certain way
>
> 2)=A0=A0=A0=A0=A0 Change/Add replication strategy
>
> 3)=A0=A0=A0=A0=A0 Change/Add some core Cassandra features
>
> 4)=A0=A0=A0=A0=A0 Use another layer in front of Cassandra =96 I=92d rathe=
r 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