On 2013-04-10 10:10:31 -0400, Tom Lane wrote: > Amit Kapila <amit.kap...@huawei.com> writes: > > On Wednesday, April 10, 2013 3:42 PM Samrat Revagade wrote: > >> Sorry, this is incorrect. Streaming replication continuous, master is not > >> waiting, whenever the master writes the data page it checks that the WAL > >> record is written in standby till that LSN. > > > I am not sure it will resolve the problem completely as your old-master can > > have some WAL extra then new-master for same timeline. I don't remember > > exactly will timeline switch feature > > take care of this extra WAL, Heikki can confirm this point? > > Also I think this can serialize flush of data pages in checkpoint/bgwriter > > which is currently not the case. > > Yeah. TBH this entire discussion seems to be "let's cripple performance > in the normal case so that we can skip doing an rsync when resurrecting > a crashed, failed-over master". This is not merely optimizing for the > wrong thing, it's positively hazardous. After a fail-over, you should > be wondering whether it's safe to resurrect the old master at all, not > about how fast you can bring it back up without validating its data. > IOW, I wouldn't consider skipping the rsync even if I had a feature > like this.
Agreed. Especially as in situations where you fall over in a planned way, e.g. for a hardware upgrade, you can avoid the need to resync with a littlebit of care. So its mostly in catastrophic situations this becomes a problem and in those you really should resync - and its a good idea not to use a normal rsync but a rsync --checksum or similar. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers