Simon Riggs wrote: > On Mon, 2005-04-18 at 21:25 -0400, Bruce Momjian wrote: > > Tom Lane wrote: > > > Simon Riggs <[EMAIL PROTECTED]> writes: > > > > The wal file could be truncated after the log switch record, though I'd > > > > want to make sure that didn't cause other problems. > > > > > > Which it would: that would break WAL file recycling. > > > > Good point. I don't see non-full WAL archiving as a problem for the > > backup or shutdown, but I do see an issue with doing archives every X > > seconds. If someone sets that really low (and someone will) we could > > easily fill the disk. > > The disk would only fill if the archiver doesn't keep up with > transmitting xlog files to the archive. The archive can fill up if it is > not correctly sized, even now. Switching log files every N seconds would > at least give a very predictable archive sizing calculation which should > actually work against users sizing their archives poorly.
I was thinking of the archiver filling because of lots of almost-empty 16mb files. If you archive every five seconds, it is 11 Gigs/hour, which is not too bad, I guess, but I would bet compression would save space and I/O load too. > > However, rather than do it ourselves, maybe we > > should make it visible to administrators so they know exactly what is > > happening and can undo it in case they need to recover, something like: > > > > > > archive_command = 'gzip <%p >%f' > > > > so the compression is done in a way that is visible to the > > administrator. > > As long as we tell them there's more than one way to do it. Many tape > drives offer hardware compression, for example, so there would be no > gain in doing this twice. Good point. I am thinking 'gzip --fast' would be the best option for copies to another file system. I see about 0.6 seconds to compress a 16mb WAL file here and I get 16x compression. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (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 7: don't forget to increase your free space map settings