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From Henrik Schröder <skro...@gmail.com>
Subject Re: Testing compaction strategies on a single production server?
Date Tue, 19 Feb 2013 17:28:52 GMT
Well, that answer didn't really help. I know how to make a survey node, and
I know how to simulate reads to it, it's just that that's a lot of work,
and I wouldn't be sure that the simulated load is the same as the
production load.

We gather a lot of metrics from our production servers, so we know exactly
how they perform over long periods of time. Changing a single server to run
a different compaction strategy would allow us to know in detail how a
different strategy would impact the cluster.

So, is it possible to modify org.apache.cassandra.db.[keyspace].[column
family].CompactionStrategyClass through jmx on a production server without
any ill effects? Or is this only possible to do on a survey node while it
is in a specific state?


/Henrik


On Tue, Feb 19, 2013 at 3:09 PM, Viktor Jevdokimov <
Viktor.Jevdokimov@adform.com> wrote:

>  Just turn off dynamic snitch on survey node and make read requests from
> it directly with CL.ONE, watch histograms, compare.****
>
> ** **
>
> Regarding switching compaction strategy there’re a lot of info already.***
> *
>
> ** **
>
> ** **
>    Best regards / Pagarbiai
> *Viktor Jevdokimov*
> Senior Developer
>
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>   *From:* Henrik Schröder [mailto:skrolle@gmail.com]
> *Sent:* Tuesday, February 19, 2013 15:57
> *To:* user
> *Subject:* Testing compaction strategies on a single production server?***
> *
>
> ** **
>
> Hey,****
>
>
> Version 1.1 of Cassandra introduced live traffic sampling, which allows
> you to measure the performance of a node without it really joining the
> cluster:
> http://www.datastax.com/dev/blog/whats-new-in-cassandra-1-1-live-traffic-sampling
> ****
>
> That page mentions that you can change the compaction strategy through jmx
> if you want to test out a different strategy on your survey node.
>
> That's great, but it doesn't give you a complete view of how your
> performance would change, since you're not doing reads from the survey
> node. But what would happen if you used jmx to change the compaction
> strategy of a column family on a single *production* node? Would that be a
> safe way to test it out or are there side-effects of doing that live?
>
> And if you do that, would running a major compaction transform the entire
> column family to the new format?****
>
> Finally, if the test was a success, how do you proceed from there? Just
> change the schema?
>
> ****
>
> /Henrik****
>

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