On Wed, 2010-06-02 at 20:28 -0400, Bruce Momjian wrote: > Simon Riggs wrote: > > On Wed, 2010-06-02 at 15:20 -0400, Bruce Momjian wrote: > > > > > The attached patch allows wal_keep_segments = -1 to keep all segements; > > > this is particularly useful for taking a base backup, where you need all > > > the WAL files during startup of the standby. I have documented this > > > usage in the patch as well. > > > > > > I am thinking of applying this after 9.0 beta2 if there is no objection. > > > > It's not clear to me why "keep all files until server breaks" is a good > > setting. Surely you would set this parameter to the size of your disk. > > Why allow it to go higher? > > Well, the -1 allows them to set it temporarily without having to compute > their free disk space. Frankly, because the disk space varies, it is > impossible to know exactly how large the disk is at the time it would > fill up. > > I think the normal computation would be: > > 1) How long is my file system backup and restore to standby > going to take > 2) How often do I generate a 16MB WAL file > > You would do some computation to figure that out, then maybe multiply it > by 10x and set that for wal_keep_segments. I figured allowing a simple > -1 would be easier.
I think its much easier to find out your free disk space than it is to calculate how much WAL might be generated during backup. Disk space doesn't vary significantly on a production database. If we encourage that laziness then we will get reports that replication doesn't work and Postgres crashes. -- Simon Riggs www.2ndQuadrant.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
