Hi, I'm currently reading through heaps of docs and web pages to learn cassandra, but there's still three questions I could not find answers for, maybe someone could help:
1. What happens, if a node is down for some time (hours, days, weeks,...) for whatever reason (hardware, power, or network failure, maintenance...) and gets back online? Does the node remain in its former state and thus become inconsistent, have outdated data, or does it update the changes that occured during its downtime from other nodes? Can nodes be easily offline for some time, then return and proceed, or do they have to be added as a fresh node replacement (of their own) to start from scratch? 2. cassandra allows to choose from several data consistency levels, especially allowing write access that does not update all nodes (i.e. QUORUM, ONE, TWO, THREE). What happens with those nodes who did not get an update? Will they synchronize with the updated nodes automatically, or will they remain in their old state (forever or until next explicit write access)? 3. What exactly happens, when a new node is added to a cluster? Will all records now belonging to the new node be automatically shifted from others? Web page http://docs.datastax.com/en/cassandra/2.0/cassandra/operations/ops_add_node_to_cluster_t.html describes a "streaming process", which sounds as if a new node was busy to collect it's belongings from others, but it also says to perform a nodetool cleanup on all the old nodes, which would "remove the keys no longer belonging to those nodes", which rather sounds like a simple drop, i.e. having those records lost. So does cassandra safely fill new nodes, or do they start as empty ones and their data is lost? Thank you! regards Hadmut
