> On 10/08/2014 07:23 AM, furu...@pm.nttdata.co.jp wrote: > >> What set of options would you pass if you want to use it as a > >> synchronous standby? And if you don't? Could we just have a single > "--synchronous" > >> flag, instead of -F and --reply-fsync? > > > > If you set "synchronous_commit" as "remote_write", the options would > be different . > > The set of options in each case, see the following. > > > > > > Synchronous standby(synchronous_commit=on) > > --fsync-interval=-1 > > --reply-fsync > > --slot=slotname > > > > Synchronous standby(synchronous_commit=remote_write) > > --fsync-interval=-1 > > --reply-fsync > > > > Asynchronous > > There are no relative options. > > > > > > Well, if the response time delay(value of > "--status-interval=interval") is acceptable, "--reply-fsync" is > unnecessary. > > Instead of "--reply-fsync", using "--synchronous"(which summarizes > the "--reply-fsync" and "fsync-interval = -1") might be easy to > understand. Although, in that case, "--fsync-interval=interval" would > be fixed value. Isn't there any problem ? > > I think we should remove --fsync-interval and --reply-fsync, and just > have a --synchronous option, which would imply the same behavior you get > with --fsync-interval=-1 --reply--fsync. > > That leaves the question of whether pg_receivexlog should do fsyncs when > it's not acting as a synchronous standby. There isn't any real need to > do so. In asynchronous mode, there are no guarantees anyway, and even > without an fsync, the OS will eventually flush the data to disk. > > But we could do even better than that. It would be best if you didn't > need even the --synchronous flag. The server knows whether the client > is a synchronous standby or not. It could tell the client.
Thanks for the reply. If we remove --fsync-interval, resoponse time to user will not be delay. Although, fsync will be executed multiple times in a short period. And there is no way to solve the problem without --fsync-interval, what should we do about it? In asynchronous mode, I think there is no problem since the specification is same with release version. > The server knows whether the client is a synchronous standby or not. > It could tell the client. When notifying the synchronous/asynchronous mode to the client from the server, do we need to change the format of the Message ? Regards, -- Furuya Osamu -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
