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From Henrik Schröder <skro...@gmail.com>
Subject Re: Testing compaction strategies on a single production server?
Date Thu, 21 Feb 2013 14:46:17 GMT
Thanks Aaron,

I hear you on the unchartered territory bit, we're definitely not gonna
risk our live data unless we know it's safe to do what we suggested. :-) Oh
well, I guess we'll have to setup a survey node instead.


/Henrik


On Thu, Feb 21, 2013 at 4:54 AM, aaron morton <aaron@thelastpickle.com>wrote:

> 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
>> Phone: +370 5 212 3063, Fax +370 5 261 0453
>> J. Jasinskio 16C, LT-01112 Vilnius, Lithuania
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>> <http://www.adform.com/site/blog/adform/adform-takes-top-spot-in-best-employer-survey/>
>>
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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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