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From "M. C. Srivas" <mcsri...@gmail.com>
Subject Re: Scan performance on a big table as combination of multiple logic tables
Date Wed, 22 Feb 2012 05:29:18 GMT
On Tue, Feb 21, 2012 at 6:16 PM, Stack <stack@duboce.net> wrote:

> On Tue, Feb 21, 2012 at 5:44 PM, M. C. Srivas <mcsrivas@gmail.com> wrote:
> > With no impact on Java GC going nuts?  FB reported (a few months ago) it
> > was bad to run a region-server
> > with -Xmx larger than 15G or 16G. Unless its no longer true, wouldn't
> that
> > be limiting factor for how
> > large one should make regions?
> >
> We don't bring the total region into memory Srivas (Is that what you
> are thinking?).

Yes,  that was my thinking ---  to do a major compaction  the region-server
would have to load all the flushed files for that region, merge them, and
then write out the new region. If the region-file was 20g in size, the
region-server would require well over 20g of heap space to do this work. Am
I completely off?

> The FB recommendation of > 15G heaps was probably the old adage around
> big heaps taking a long time to sweep when GCing?
> Good on you,
> St.Ack

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