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From Eric Newton <eric.new...@gmail.com>
Subject Re: Accumulo Caching for benchmarking
Date Sat, 04 Aug 2012 11:19:04 GMT
You can drop the OS caches between runs:

# echo 1 > /proc/sys/vm/drop_caches


On Fri, Aug 3, 2012 at 9:41 PM, Christopher Tubbs <ctubbsii@gmail.com>wrote:

> Steve-
>
> I would probably design the experiment to test different cluster sizes
> as completely independent. That means, taking the entire thing down
> and back up again (possibly even rebooting the boxes, and/or
> re-initializing the cluster at the new size). I'd also do several runs
> while it is up at a particular cluster size, to capture any
> performance difference between the first and a later run due to OS or
> TServer caching, for analysis later.
>
> Essentially, when in doubt, take more data...
>
> --L
>
>
> On Fri, Aug 3, 2012 at 5:50 PM, Steven Troxell <steven.troxell@gmail.com>
> wrote:
> > Hi  all,
> >
> > I am running a benchmarking project on accumulo looking at RDF queries
> for
> > clusters with different node sizes.   While I intend to look at caching
> for
> > each optimizing each individual run, I do NOT want caching to interfere
> for
> > example between runs involving the use of 10 and 8 tablet servers.
> >
> > Up to now I'd just been killing nodes via the bin/stop-here.sh script
> but I
> > realize that may have allowed caching from previous runs with different
> node
> > sizes to influence my results.   It seemed weird to me for exmaple when I
> > realized dropping nodes actually increased performance (as measured by
> query
> > return times) in some cases (though I acknowledge the code I'm working
> with
> > has some serious issues with how ineffectively it is actually utilizing
> > accumulo, but that's an issue I intend to address later).
> >
> > I suppose one way would be between a change of node sizes,  stop and
> restart
> > ALL nodes ( as opposed to what I'd been doing in just killing 2 nodes for
> > example in transitioning from a 10 to 8 node test).  Will this be sure to
> > clear the influence of caching across runs, and is there any cleaner way
> to
> > do this?
> >
> > thanks,
> > Steve
>

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