How Cassandra handle part of cluster desynchronization?

What is going one when parts of the cluster don't see each other?

For example: when 3/7 of cluster can't communicate with 4/7 cluster for coupe of hours.

Each part of cluster use "hinted handof" for other one part?

The data is reba开发者_如何学JAVAlanced and replicated in each part of cluster?

If I balance clients to each part of cluster for writes, after join parts of cluster there will by data lost?

yes, writes to any replica will be replicated to the others once the partition heals. http://wiki.apache.org/cassandra/HintedHandoff, http://wiki.apache.org/cassandra/ReadRepair, and http://wiki.apache.org/cassandra/ArchitectureAntiEntropy all play a role with this.

you can also specify QUORUM or higher ConsistencyLevel and then only writes (or reads) that can see a majority of the replicas will succeed.