Using as a pretext a comparison with MongoDB — why MongoDB? — Sergei Tsarev provides some details about Clustrix data distribution, fault tolerance, and availability models.
At Clustrix, we think that Consistency, Availability, and Performance are much more important than Partition tolerance. Within a cluster, Clustrix keeps availability in the face of node loss while keeping strong consistency guarantees. But we do require that more than half of the nodes in the cluster group membership are online before accepting any user requests. So a cluster provides fully ACID compliant transactional semantics while keeping a high level of performance, but you need majority of the nodes online.
Original title and link: Clustrix: Distribution, Fault Tolerance, and Availability Models (NoSQL databases © myNoSQL)