Create one big happy love in keyspace. Use the key structure to identify the different clients data. 

The is more support for multi tenancy systems but a lot of the memory configuration is per keyspace/column family, so you cannot run that many keyspaces. 

This page has some more information http://wiki.apache.org/cassandra/MultiTenant

Aaron


On 03 Sep, 2010,at 01:25 PM, Mike Peters <cassandra@softwareprojects.com> wrote:

Hi,

We're in the process of migrating 4,000 MySQL client databases to
Cassandra. All database schemas are identical.

With MySQL, we used to provision a separate 'database' per each client,
to make it easier to shard and move things around.

Does it make sense to migrate the 4,000 MySQL databases to 4,000
keyspaces in Cassandra? Or should we stick with a single keyspace?

My concerns are -
#1. Will every single node end up with 4k folders under /cassandra/data/?

#2. Performance: Will Cassandra work better with a single keyspace +
lots of keys, or thousands of keyspaces?

-

Granted it's 'cleaner' to have a separate keyspace per each client, but
maybe that's not the best approach with Cassandra.

Thoughts?