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From Rob Coli <rc...@digg.com>
Subject Re: Node OOM Problems
Date Mon, 23 Aug 2010 19:24:27 GMT
On 8/22/10 12:00 AM, Wayne wrote:
> Due to compaction being so expensive in terms of disk resources, does it
> make more sense to have 2 data volumes instead of one? We have 4 data
> disks in raid 0, would this make more sense to be 2 x 2 disks in raid 0?
> That way the reader and writer I assume would always be a different set
> of spindles?

Cassandra supports multiple data directories via specifying multiple 
DataFileDirectory items in the DataFileDirectories block. Unfortunately 
due to the way that compaction currently works, this often results in 
one or the other drive being much hotter than the other and lots of 
inter-disk shuffling of data.

https://issues.apache.org/jira/browse/CASSANDRA-897

Is a JIRA which refers to these issues. I am not aware of anyone who has 
successfully improved their overall performance via multiple data 
directories. I am, however, aware of people who have encountered 
negative consequences as a result of doing so. As such, I do not 
recommend it.

=Rob


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