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From Omar Shibli <o...@eyeviewdigital.com>
Subject Re: How to avoid inter-dc read requests
Date Tue, 23 Jul 2013 12:22:03 GMT
I simply monitor the load avg of the nodes using opscenter.
I started with idle nodes (by idle I mean load avg of all nodes < 1.0),
then started to run a lot of key slice read requests on *"analytic" DC *with
CL local quorum (I also made sure that the client worked with only
with analytic DC), after a few minutes I noticed that the load avg of all
the nodes increased dramatically (>10).

Thanks in Advance Aaron,

On Tue, Jul 23, 2013 at 12:02 PM, aaron morton <aaron@thelastpickle.com>wrote:

> > All the read/write request are issued with CL local quorum, but still
> there're a lot of inter-dc read request.
> >
> How are you measuring this ?
>
> Cheers
>
> -----------------
> Aaron Morton
> Cassandra Consultant
> New Zealand
>
> @aaronmorton
> http://www.thelastpickle.com
>
> On 22/07/2013, at 8:41 AM, sankalp kohli <kohlisankalp@gmail.com> wrote:
>
> > Slice query does not trigger background read repair.
> > Implement Read Repair on Range Queries
> >
> >
> > On Sun, Jul 21, 2013 at 1:40 PM, sankalp kohli <kohlisankalp@gmail.com>
> wrote:
> > There can be multiple reasons for that
> > 1) Background read repairs.
> > 2) Your data is not consistent and leading to read repairs.
> > 3) For writes, irrespective of the consistency used, a single write
> request will goto other DC
> > 4) You might be running other nodetools commands like repair.
> > read_repair_chanceĀ¶
> >
> > (Default: 0.1 or 1) Specifies the probability with which read repairs
> should be invoked on non-quorum reads. The value must be between 0 and 1.
> For tables created in versions of Cassandra before 1.0, it defaults to 1.
> For tables created in versions of Cassandra 1.0 and higher, it defaults to
> 0.1. However, for Cassandra 1.0, the default is 1.0 if you use CLI or any
> Thrift client, such as Hector or pycassa, and is 0.1 if you use CQL.
> >
> >
> >
> > On Sun, Jul 21, 2013 at 10:26 AM, Omar Shibli <omar@eyeviewdigital.com>
> wrote:
> > One more thing, I'm doing a lot of key slice read requests, is that
> supposed to change anything?
> >
> >
> > On Sun, Jul 21, 2013 at 8:21 PM, Omar Shibli <omar@eyeviewdigital.com>
> wrote:
> > I'm seeing a lot of inter-dc read requests, although I've followed
> DataStax guidelines for multi-dc deployment
> http://www.datastax.com/dev/blog/deploying-cassandra-across-multiple-data-centers
> >
> > Here is my setup:
> > 2 data centers within the same region (AWS)
> > Targeting DC, RP 3, 6 nodes
> > Analytic DC, RP 3, 11 nodes
> >
> > All the read/write request are issued with CL local quorum, but still
> there're a lot of inter-dc read request.
> > Any suggestion, or am I missing something?
> >
> > Thanks in advance,
> >
> >
> >
>
>

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