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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: memory_locking_policy parameter in cassandra.yaml for disabling swap - has this variable been renamed?
Date Thu, 28 Jul 2011 12:52:12 GMT
This is not advisable in general, since non-mmap'd I/O is substantially slower.

The OP is correct that it is best to disable swap entirely, and
second-best to enable JNA for mlockall.

On Thu, Jul 28, 2011 at 7:05 AM, Adi <adi.pandit@gmail.com> wrote:
>> Hi,
>>
>>
>>
>> We’ve started having problems with cassandra and memory swapping on linux
>> which seems to be a fairly common issue (in our particular case after about
>> a week all swap space will have been used up and we have to restart the
>> process).
>>
>>
>>
>> It sounds like the general consensus is to just disable swap completely,
>> but the recently released “Cassandra High Performance Cookbook” from Packt
>> has instructions for “Stopping cassandra from using swap without disabling
>> it system wide”. We’ve tried following the instructions but it refers to a
>> “memory_locking_policy” variable in cassandra.yaml which throws an “unknown
>> property” error on startup and I can’t find any reference to it in any of
>> the cassandra docs.
>>
>>
>>
>> I’ve copied the summarised instructions below, does anyone know if this is
>> something that ever worked or is there a different variable to set which
>> does the same thing?
>
> If you are having trouble preventing the swapping the other parameter that
> can help is disk_access_mode
> We are using "mmap_index_only" and that has prevented swapping for now.
> "auto" will try to use mmap for all disk access ,
> "mmap" will use mmap
> "standard" will not use mmap
>
> Search for swapping on the users list and go through the email discussions
> and jira issues related to swapping and that will give you an idea what can
> work for you.
> -Adi



-- 
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of DataStax, the source for professional Cassandra support
http://www.datastax.com

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