Hm... I understand that RAID0 would help to create a bigger pool for compactions. However, it might impact read performance: if I have several CF's (with their SSTables), random read requests for the CF files that are on separate disks will behave nicely - however if it's RAID0 then a random read on any file will create a random read on all of the hard disks. Correct?

-Roland

2010/4/26 Jonathan Ellis <jbellis@gmail.com>
http://wiki.apache.org/cassandra/CassandraHardware

On Mon, Apr 26, 2010 at 1:06 PM, Edmond Lau <edmond@ooyala.com> wrote:
> Ryan -
>
> You (or maybe someone else) mentioned using RAID-0 instead of multiple
> data directories at the Cassandra hackathon as well.  Could you
> explain the motivation behind that?
>
> Thanks,
> Edmond
>
> On Mon, Apr 26, 2010 at 9:53 AM, Ryan King <ryan@twitter.com> wrote:
>> I would recommend using RAID-0 rather that multiple data directories.
>>
>> -ryan
>>
>> 2010/4/26 Roland Hänel <roland@haenel.me>:
>>> I have a configuration like this:
>>>
>>>   <DataFileDirectories>
>>>       <DataFileDirectory>/storage01/cassandra/data</DataFileDirectory>
>>>       <DataFileDirectory>/storage02/cassandra/data</DataFileDirectory>
>>>       <DataFileDirectory>/storage03/cassandra/data</DataFileDirectory>
>>>   </DataFileDirectories>
>>>
>>> After loading a big chunk of data into cassandra, I end up wich some 70GB in
>>> the first directory, and only about 10GB in the second and third one. All
>>> rows are quite small, so it's not just some big rows that contain the
>>> majority of data.
>>>
>>> Does Cassandra have the ability to 'see' the maximum available space in
>>> these directory? I'm asking myself this question since my limit is 100GB,
>>> and the first directory is approaching this limit...
>>>
>>> And, wouldn't it be better if Cassandra tried to 'load-balance' the files
>>> inside the directories because this will result in better (read) performance
>>> if the directories are on different disks (which is the case for me)?
>>>
>>> Any help is appreciated.
>>>
>>> Roland
>>>
>>>
>>
>