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From James Golick <jamesgol...@gmail.com>
Subject Re: Instability and memory problems
Date Mon, 21 Jun 2010 17:15:01 GMT
On Mon, Jun 21, 2010 at 12:24 PM, Peter Schuller <
peter.schuller@infidyne.com> wrote:

> > Just an update here. We're now entirely on standard IO mode, and
> everything
> > is stable and happy. There hasn't been much of a performance hit, if at
> all.
>
> Cool. Just be aware that if my speculation was correct that you're (1)
> dedicating a very large portion of system memory to cassandra, but (2)
> most of that is unused in the sense of being live, you are probably
> going to see more disk I/O on reads than you would otherwise due to
> less data fitting in cache (assuming your access pattern has some kind
> of locality to make caching effective, and assuming you did not crank
> up the in-JVM caching when switching to standard I/O mode).
>

Of course. We've got about 75% of available memory dedicated to Cassandra
row caches which leaves just under 6GB for fs caches, which is just under
10% of the load on the machine. We're probably going to put a lot more
memory in these nodes at this point.


>
> --
> / Peter Schuller
>

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