Technically, key spaces themselves are relatively cheap, so there is no limit there per se. But... you probably want to put tables in them, which are not so cheap. Generally, the guidance is for no more than “low hundreds” of tables, regardless of whether you have one table per key space or all in one key space.
If you want to go beyond “low hundreds” of tables, tread carefully. The official line is that “Although having more than dozens or hundreds of tables defined is almost certainly a Bad Idea (just as it is a design smell in a relational database), it's relatively straightforward to allow disabling the SlabAllocator.” Emphasis on “almost certainly a Bad Idea.” See: https://issues.apache.org/jira/browse/CASSANDRA-5935 “Allow disabling slab allocation” -- Jack Krupansky From: Sourabh Agrawal Sent: Thursday, July 10, 2014 11:22 PM To: user@cassandra.apache.org Subject: Practical limit to number of keyspaces? Hi, We are using 2.0.x in production env. Each node has 8G heap. Is there a practical limit to how many keyspaces I can have? Please note that many keyspaces remain mostly dormant while others have very high level of activity. -- Sourabh Agrawal Bangalore +91 9945657973
