Hello Satoshi and the community, I am also using commitlog_sync for durability, but I have never modified commitlog_sync_batch_window_in_ms parameter yet, so I wondered if it is working or not.
As Satoshi said, I also changed commitlog_sync_batch_window_in_ms (to 10000) and restarted C* and issued some INSERT command. But, it actually returned immediately right after issuing. So, it seems like the parameter is not working correctly. Are we missing something ? Thanks, Hiro On Thu, Oct 27, 2016 at 5:58 PM, Satoshi Hikida <sahik...@gmail.com> wrote: > Hi, all. > > I have a question about "batch" commit log sync behavior with C* version > 2.2.8. > > Here's what I have done: > > * set commitlog_sync to the "batch" mode as follows: > >> commitlog_sync: batch >> commitlog_sync_batch_window_in_ms: 10000 > > * ran a script which inserts the data to a table > * prepared a disk dedicated to store the commit logs > > According to the DataStax document, I expected that fsync is done once in a > batch window (one fsync per 10sec in this case) and writes issued within > this batch window are blocked until fsync is completed. > > In my experiment, however, it seems that the write requests returned almost > immediately (within 300~400 ms). > > Am I misunderstanding something? If so, can someone give me any advices as > to the reason why C* behaves like this? > > > I referred to this document: > https://docs.datastax.com/en/cassandra/2.2/cassandra/configuration/configCassandra_yaml.html#configCassandra_yaml__PerformanceTuningProps > > Regards, > Satoshi >
