Is the on-disk format already settled? I've thought to try betas but impossibility to upgrade to 1.1 release stopped me.

2012/4/13 Sylvain Lebresne <sylvain@datastax.com>
The Cassandra team is pleased to announce the release of the first release
candidate for the future Apache Cassandra 1.1.


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Best regards,
 Vitalii Tymchyshyn