Simon Riggs wrote: > On Wed, 2004-07-14 at 10:57, Zeugswetter Andreas SB SD wrote: > > > The recovery mechanism doesn't rely upon you knowing 1 or 3. The > > > recovery reads pg_control (from the backup) and then attempts to > > > de-archive the appropriate xlog segment file and then starts > > > rollforward > > > > Unfortunately this only works if pg_control was the first file to be > > backed up (or by chance no checkpoint happened after backup start and > > pg_control backup) > > > > Other db's have commands for: > > start/end external backup > > > > OK...this idea has come up a few times. Here's my take: > > - OS and hardware facilities exist now to make instant copies of sets of > files. Some of these are open source, others not. If you use these, you > have no requirement for this functionality....but these alone are no > replacement for archive recovery.... I accept that some people may not > wish to go to the expense or effort to use those options, but in my mind > these are the people that will not be using archive_mode anyway. > > - all we would really need to do is to stop the bgwriter from doing > anything during backup. pgcontrol is only updated at checkpoint. The > current xlog is updated constantly, but this need not be copied because > we are already archiving it as soon as its full. That leaves the > bgwriter, which is now responsible for both lazy writing and > checkpoints. > So, put a switch into bgwriter to halt for a period, then turn it back > on at the end. Could be a SIGHUP GUC...or...
I don't think we can turn off all file system writes during a backup. Imagine writing to a tape. Preventing file system writes would make the system useless. > - please could somebody else code that?... my time is limited Yes, I think someone else could code this. -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faqs/FAQ.html
