There is a discrepancy between the two documentation: http://wiki.apache.org/cassandra/Durability
Cassandra's default configuration sets the commitlog_sync mode to periodic, > causing the commitlog to be synced every commitlog_sync_period_in_ms > milliseconds, > so you can potentially lose up to that much data if all replicas crash > within that window of time. > http://www.datastax.com/documentation/cassandra/2.0/cassandra/dml/dml_durability_c.html Writes in Cassandra are durable. All writes to a replica node are recorded > both in memory and in a commit log on disk before they are acknowledged as > a success. If a crash or server failure occurs before the memory tables are > flushed to disk, the commit log is replayed on restart to recover any lost > writes. > I wonder which is correct? Does Cassandra (default configuration) wait till it persists the update to its commit log before it acks back the write? or doesn't it? I wonder what happens if due to power outage all replicas die at the same time? Can such a power outage cause writes kept in memory within that 10 second window to be lost? Mohica
