On Wed, Apr 23, 2014 at 8:08 AM, Mohica Jasha <mohica.ja...@gmail.com>wrote:
> 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? > Yes. Unless you set Cassandra to operate with a batch commit log that doesn't ack until fsync after every batch of writes, you can lose un-fsynced data from the commitlog. As an additional wrinkle, in 2.0 the behavior is slightly different from the expectation from the documentation, as of 2.1 it behaves as one would expect from the documentation of "batch". https://issues.apache.org/jira/browse/CASSANDRA-3578 Is an issue related to the changes in this behavior, but per belliotsmith he's not sure if this is where it's fully discussed. =Rob PS - I have bcc:ed docs AT datastax for their information; in general they are quite responsive to requests of this nature, they value correctness and clarity in their docs. :D
