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From aaron morton <aa...@thelastpickle.com>
Subject Re: Testing compaction strategies on a single production server?
Date Thu, 21 Feb 2013 03:54:48 GMT
I *think* it will work. The steps in the blog post to change the compaction strategy before
RING_DELAY expires is to ensure no sstables are created before the strategy is changed. 

But I think you will be venturing into unchartered territory where their might be dragons.
And not the fun Disney kind.

While it may be more work I personally would use one node in write survey to test LCS 

Cheers

-----------------
Aaron Morton
Freelance Cassandra Developer
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 20/02/2013, at 6:28 AM, Henrik Schröder <skrolle@gmail.com> wrote:

> 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
> 
> Email: Viktor.Jevdokimov@adform.com
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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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