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From aaron morton <aa...@thelastpickle.com>
Subject Re: how to increase compaction rate?
Date Mon, 12 Mar 2012 09:44:50 GMT
> I don't understand why I
> don't get multiple concurrent compactions running, that's what would
> make the biggest performance difference.
concurrent_compactors
Controls how many concurrent compactions to run, by default it's the number of cores on the
machine. 

If you are not CPU bound check iostats (http://spyced.blogspot.co.nz/2010/01/linux-performance-basics.html_)


Cheers
-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 12/03/2012, at 7:21 PM, Thorsten von Eicken wrote:

> On 3/11/2012 9:17 PM, Peter Schuller wrote:
>>> multithreaded_compaction: false
>> Set to true.
> I did try that. I didn't see it go any faster. The cpu load was lower,
> which I assumed meant fewer bytes/sec being compressed
> (SnappyCompressor). I didn't see multiple compactions in parallel.
> Nodetool compactionstats behaved strange and instead of showing
> individual compactions with a %-complete it showed a running count of
> total bytes compacted. (Darn, I don't have the output of that anymore in
> my terminal buffer.) It just didn't look good to me. Are you positive
> that it is faster with leveled compaction? I don't understand why I
> don't get multiple concurrent compactions running, that's what would
> make the biggest performance difference. Is the compaction parallelism
> perhaps only across multiple CFs? That would explain what I see.
> 
> Thorsten


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