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From Amit Sinha <>
Subject Re: Cassandra committing massive virtual memory
Date Thu, 22 Jul 2010 14:30:28 GMT
The DiskAccessMode is set to auto.
I am going to try with standard and see, but i am concerned how much that
would affect performance negatively.


On Wed, Jul 21, 2010 at 3:59 PM, Aaron Morton <>wrote:

> Are you using mmap or auto DiskAccessMode ?
> There is a known issue with memory mapped file access taking up a lot of
> memory. See CASSANDRA-1214
> there is also some
> discussion in the mail list here.
> Try setting the DiskAccessMode to standard
> Aaron
> On 22 Jul, 2010,at 10:37 AM, Amit Sinha <> wrote:
> We are seeing cassandra using very high virtual memory. One server in the
> cluster shows 90GB and the other shows about 70GB of committed virtual
> memory.
> The real memory used is less than 1GB. The Xmx is 4GB. The physical memory
> on the machine is 32GB and the swap space on the machine is around 20GB.
> I understand that the virtual memory is not really used by the process and
> is just reserved. My question is why does cassandra need to reserve such
> huge memory. What is the logic that is used internally. How is it related to
> usage pattern or data storage pattern. Should we be concerned?
> thanks
> Amit


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