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From aaron morton <aa...@thelastpickle.com>
Subject Re: How to avoid inter-dc read requests
Date Thu, 25 Jul 2013 05:06:48 GMT
That does not measure what the servers are doing though.

Track the number of reads per CF, it's exposed with nodetool cfstats and is in ops centre
as well. 

Cheers 
-----------------
Aaron Morton
Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 24/07/2013, at 12:22 AM, Omar Shibli <omar@eyeviewdigital.com> wrote:

> 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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