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From Edward Capriolo <edlinuxg...@gmail.com>
Subject Re: Question on using consistency level with NetworkTopologyStrategy
Date Thu, 08 Sep 2011 22:22:25 GMT
On Thu, Sep 8, 2011 at 4:14 PM, Anand Somani <meatforums@gmail.com> wrote:

> Hi,
>
> Have a requirement, where data is spread across multiple DC for disaster
> recovery. So I would use the NTS, that is clear, but I have some questions
> with this scenario
>
>    - I have 2 Data Centers
>    - RF - 2 (active DC) , 2 (passive DC)
>    - with NTS - Consistency level options are - LOCAL_QUORUM and EACH
>    _QUORUM
>    - I want LOCAL_QUORUM and 1 remote copy (not 2) for write to succeed,
>    if I used EACH_QUORUM - it would mean that I need both the remote nodes up
>    (as I understand from
>    http://www.datastax.com/docs/0.8/operations/datacenter).
>
> So if that is my requirement what consistency Level should I be using for
> my writes? Is that even possible with NTS or another strategy? I could use
> the SimpleStrategy with Quorum, but that would mean sending 2 copies
> (instead of 1 per DC that NTS uses to optimize on WAN traffic) to remote DC
> (since it does not understand DC's)?
>
> Thanks
> Anand
>

Cassandra may not be doing what you think.

QUORUM levels work oddly with less then 3 replicas.

You will probably will get closest to what you want with CL.TWO or
CL.THREE.

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