Hi, On Mon, Apr 6, 2009 at 11:13 PM, Andreas Pflug <pgad...@pse-consulting.de> wrote: > Scott Mead wrote: >> >> >> >> On Mon, Apr 6, 2009 at 7:37 AM, Andreas Pflug >> <pgad...@pse-consulting.de <mailto:pgad...@pse-consulting.de>> wrote: >> >> Running 8.3.7, I have a warm standby configuration with a >> archive_timeout of 10min. >> >> It's obvious that there's a 10min period where data could be lost >> if the >> master fails and the warm standby server has to take over. What's not >> obvious is that this is true even if the master server is shut down >> regularly, because it will not write out a last log segment to the >> archive. As a consequence, when doing a controlled failover (for >> maintenance purposes or so) all data changed after the last >> archive copy >> will be lost. >> IMHO this should be mentioned in the docs explicitly (I find it quite >> surprising that data can be lost even if the system is shutdown >> correctly), or better when shutting down the postmaster should >> spit all >> log segments containing all changes when archiving is on so the warm >> standby server can catch up. >> >> >> >> You make an excellent point. If you're looking for a way to mitigate >> this risk, run: >> >> select pg_switch_xlog() ; >> >> Before shutting down. > Sort of, unless some other user succeeds to commit a transaction after > pg_switch_xlog, and before the database ceases operation. > > My "graceful failover" procedure now includes this workaround: > - shutdown server > - restart server with --listen_addresses='' to prevent other users to > connect (there are no local users on the server machine) > - pg_switch_xlog() > - shutdown finally > - let the warm server continue
What if new xlogs are generated by autovacuum or bgwriter between pg_switch_xlog and final shutdown? Those xlogs can be ignored? Regards, -- Fujii Masao NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
