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From Edward Capriolo <edlinuxg...@gmail.com>
Subject Re: compaction strategy
Date Sat, 07 May 2011 15:51:22 GMT
On Sat, May 7, 2011 at 8:54 AM, Jonathan Ellis <jbellis@gmail.com> wrote:
> On Sat, May 7, 2011 at 2:01 AM, Terje Marthinussen
> <tmarthinussen@gmail.com> wrote:
>> 1. Would it make sense to make full compactions occur a bit more aggressive.
>
> I'd rather reduce the performance impact of being behind, than do more
> full compactions: https://issues.apache.org/jira/browse/CASSANDRA-2498
>
>> 2. I
>> would think the code should be smart enough to either trigger a full
>> compaction and scrap the current queue, or at least merge some of those
>> pending tasks into larger ones
>
> Not crazy but a queue-rewriter would be nontrivial. For now I'm okay
> with saying "add capacity until compaction can mostly keep up." (Most
> people's problem is making compaction LESS aggressive, hence
> https://issues.apache.org/jira/browse/CASSANDRA-2156.)
>
> --
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of DataStax, the source for professional Cassandra support
> http://www.datastax.com
>

Adjusting compaction and memtable settings is a tuning thing. Tuning
is not usually a game changer. Every once in a while you hit a
something wonderful and get 20% or 30% enhancement. But normally you
are in the gain 1%-3% range.

If you are seeing 600 pending compaction tasks regularly you almost
definitely need more hardware.

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