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Date: Fri, 11 Oct 2013 13:06:14 -0700
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Subject: Re: Heap requirement for Off-heap space
From: Robert Coli <rcoli@eventbrite.com>
To: "user@cassandra.apache.org" <user@cassandra.apache.org>
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On Fri, Oct 11, 2013 at 5:47 AM, Artur Kronenberg <
artur.kronenberg@openmarket.com> wrote:

> I was playing around with cassandra off-heap options. I configured 3 GB
> off-heap for my row cache and 2 GB Heap space for cassandra.
>

The row cache is only really useful in very specific cases involving very
small, hot, and uniform in size datasets. Many more people have shot
themselves in the foot by using it than have had great success.

The off-heap row cache also invalidates on UPDATE, which is significantly
different from what many people expect.


> Is there a formula that maps heap space to off-heap?


FWIW, I'd also like to know the answer to this question.

=Rob

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<div dir=3D"ltr">On Fri, Oct 11, 2013 at 5:47 AM, Artur Kronenberg <span di=
r=3D"ltr">&lt;<a href=3D"mailto:artur.kronenberg@openmarket.com" target=3D"=
_blank">artur.kronenberg@openmarket.com</a>&gt;</span> wrote:<br><div class=
=3D"gmail_extra">
<div class=3D"gmail_quote"><blockquote class=3D"gmail_quote" style=3D"margi=
n:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I was playing aro=
und with cassandra off-heap options. I configured 3 GB off-heap for my row =
cache and 2 GB Heap space for cassandra.<br>
</blockquote><div><br></div><div>The row cache is only really useful in ver=
y specific cases involving very small, hot, and uniform in size datasets. M=
any more people have shot themselves in the foot by using it than have had =
great success.</div>
<div><br></div><div>The off-heap row cache also invalidates on UPDATE, whic=
h is significantly different from what many people expect.=A0</div><div>=A0=
</div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-l=
eft:1px #ccc solid;padding-left:1ex">

Is there a formula that maps heap space to off-heap?</blockquote><div><br><=
/div><div>FWIW, I&#39;d also like to know the answer to this question.</div=
><div><br></div><div>=3DRob</div></div></div></div>

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