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From Utku Can Top├žu <>
Subject Re: Tuning cassandra to use less memory
Date Wed, 06 Oct 2010 16:05:33 GMT
Hi Oleg,

I've been also looking into these after some research.

I've been tacking with:
1. Setting the default max and min heap from 1G to 1500M.
2. I'm not using row caches, and the key caches are set to 1000, before they
were 200K as default
3. I've lowered the memtable throughput to 32MB
4. We're using a 32-bit JVM

- And additionally I've changed the disk access mode to mmap_index_only
(this was the only suggested ).
- I've also stopped using OPP and switched to RP

In our system there are currently 4 nodes, and there's one active keysapce
containing 12 active standart columnfamilies.

The nodes are still swapping, even though the swappiness is set to zero
right now. After swapping comes the OOM.

I'm not so sure about what to do but the 1.7 G does not seem to fit our
Do you think so?


On Wed, Oct 6, 2010 at 12:47 PM, Oleg Anastasyev <> wrote:

> >
> > Hi All,We're currently starting to get OOM exceptions in our cluster. I'm
> trying to push the limiations of our machines. Currently we have 1.7 G
> memory
> (ec2-medium)I'm wondering if by tweaking some of cassandra's configuration
> settings, is it possible to make it live in peace and less memory.
> 1. What is current java heap size on your nodes ? Is it default 1Gb ? Try
> to
> configure more.
> 2. Do you use row or key caches ? Try to lower their sizes in
> configuration.
> 3. What are memtable throughput mb threshold ? You can try to lower it.
> 4. Do you use 32-bit or 64-bit VM ? For 1.7Gb RAM size 32-bit VM is enough
> and
> it uses less RAM. so you can give more to Java heap.

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