Using a single directory will make be the most efficient use of space, multi directories are useful when you accidentally run out of space http://www.mail-archive.com/user@cassandra.apache.org/msg07874.html

Can you put the SSD's in a stripe set ? 

Also this may be of interest http://www.bitplumber.net/2010/10/a-cassandra-hardware-stack-dell-c1100s-ocz-vertex-2-ssds-with-sandforce-arista-7048s/

Aaron

On 4 Apr 2011, at 02:32, Anurag Gujral wrote:

Now it is using all the three disks . I want to understand why recommended approach is to use
one single large volume /directory and not multiple ones,can you please explain in detail.
I am using SSDs using  three small ones is cheaper than using one large one.
Please Suggest
Thanks
Anurag

On Sun, Apr 3, 2011 at 7:31 AM, aaron morton <aaron@thelastpickle.com> wrote:
Is this still a problem ? Are you getting errors on the server ?

It should be choosing the directory with the most space.

btw, the recommended approach is to use a single large volume/directory for the data.

Aaron

On 2 Apr 2011, at 01:56, Anurag Gujral wrote:

> Hi All,
>           I have setup a cassandra cluster with three data directories but cassandra is using only one of them and that disk is out of space
> and .Why is cassandra not using all the three data directories.
>
> Plz Suggest.
>
> Thanks
> Anurag