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?

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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.