Shane Ambler wrote: > Dawid Kuroczko wrote: > >On 10/20/06, Shane Ambler <pgsql@xxxxxxxxxxxxxxxx> wrote: > > >>The one thing worse than kill -9 the postmaster is pulling the power > >>cord out of the server. Which is what makes UPS's so good. > > > > > >Well, I think that pulling the power cord is much safer than killing -9 > >the postmaster. If you pull the plug, then during bootup postgresql > >will just replay every COMMITed transaction, so there won't be any > >dataloss or downtime. > > If you kill -9 the postmaster the system can still finish sending > changes to disk and close the file but pulling the power cord can stop a > write in the middle of a block giving you half new data and half old > data in the one file. That case is protected against in the WAL code. That's what we save whole page images for. The only difference between kill -9 postmaster and abrupt shutdown, is that on the former case there may be backends that continue to run and commit transactions. Those will still be WAL-logged though. -- Alvaro Herrera http://www.CommandPrompt.com/ The PostgreSQL Company - Command Prompt, Inc.
