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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Tuning a column family for archival
Date Thu, 11 Aug 2011 20:09:10 GMT
No.  He's saying that one of the points of mmaping the data files is
that the OS is free to only keep files that are actually used, in the
page cache.  Since this data is backed by an actual file swap is not
involved.

On Thu, Aug 11, 2011 at 12:59 PM, Jason Baker <jason@apture.com> wrote:
> On Thu, Aug 11, 2011 at 6:14 AM, Edward Capriolo <edlinuxguru@gmail.com>
> wrote:
>>
>> In many regards Cassandra automatically does the correct thing. Other then
>> the costs of the bloom filters for the table size being in ram, if you never
>> read or write to those sstables and you are not reusing the row key, the OS
>> will page out those tables and they will not take any cache space.
>
> Forgive me if I'm being dense, but the wiki says that an instance shouldn't
> be swapping at all[1].  I presently have swappiness turned down to 0.  Are
> you saying that there may be benefits to allowing some swap usage?
> [1] http://wiki.apache.org/cassandra/MemtableThresholds?highlight=%28swap%29#Virtual_Memory_and_Swap



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

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