Dimitri Fontaine wrote: > Le 15 juil. 09 à 23:03, Heikki Linnakangas a écrit : >> 2. The primary should have no business reading back from the archive. >> The standby can read from the archive, as it can today. > > Sorry to insist, but I'm not sold on your consensus here, yet: > http://archives.postgresql.org/pgsql-hackers/2009-07/msg00486.php > > There's a true need for the solution to be simple to install, and > providing a side channel for the standby to go read the archives itself > isn't it.
I think a better way to address that need is to provide a built-in mechanism for the standby to request a base backup and have it sent over the wire. That makes the initial setup very easy. > Furthermore, the counter-argument against having the primary > able to send data from the archives to some standby is that it should > still work when primary's dead, but as this is only done in the setup > phase, I don't see that being able to continue preparing a not-yet-ready > standby against a dead primary is buying us anything. The situation arises also when the standby falls badly behind. A simple solution to that is to add a switch in the master to specify "always keep X MB of WAL in pg_xlog". The standby will then still find it in pg_xlog, making it harder for a standby to fall so much behind that it can't find the WAL it needs in the primary anymore. Tom suggested that we can just give up and re-sync with a new base backup, but that really requires built-in base backup capability, and is only practical for small databases. I think we should definitely have both those features, but it's not urgent. The replication works without them, although requires that you set up traditional archiving as well. -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
