It seems like you could use a composite key partioner to accomplish this

On Monday, November 7, 2011, Daniel Doubleday <daniel.doubleday@gmx.net> wrote:
> Allow for deterministic / manual sharding of rows.
>
> Right now it seems that there is no way to force rows with different row keys will be stored on the same nodes in the ring.
> This is our number one reason why we get data inconsistencies when nodes fail.
>
> Sometimes a logical transaction requires writing rows with different row keys. If we could use something like this:
>
> prefix.uniquekey and let the partitioner use only the prefix the probability that only part of the transaction would be written could be reduced considerably.
>
>
>
> On Nov 1, 2011, at 11:59 PM, Jonathan Ellis wrote:
>
>> Hi all,
>>
>> Two years ago I asked for Cassandra use cases and feature requests.
>> [1]  The results [2] have been extremely useful in setting and
>> prioritizing goals for Cassandra development.  But with the release of
>> 1.0 we've accomplished basically everything from our original wish
>> list. [3]
>>
>> I'd love to hear from modern Cassandra users again, especially if
>> you're usually a quiet lurker.  What does Cassandra do well?  What are
>> your pain points?  What's your feature wish list?
>>
>> As before, if you're in stealth mode or don't want to say anything in
>> public, feel free to reply to me privately and I will keep it off the
>> record.
>>
>> [1] http://www.mail-archive.com/cassandra-dev@incubator.apache.org/msg01148.html
>> [2] http://www.mail-archive.com/cassandra-user@incubator.apache.org/msg01446.html
>> [3] http://www.mail-archive.com/dev@cassandra.apache.org/msg01524.html
>>
>> --
>> Jonathan Ellis
>> Project Chair, Apache Cassandra
>> co-founder of DataStax, the source for professional Cassandra support
>> http://www.datastax.com
>
>