Re: Replication and PITR

Csaba Nagy wrote:

Cons:     

- No reliability.  On slow days, WAL logs could take a long time to rotate, so small but important transactions might not be replicated for a long time.   

That's gone with 8.2, it will be possible to stream the last
modifications, or force a WAL recycle periodically, whatever fits you
better. There is some new infrastructure which allows these things,
although I didn't have the time to play with them. 

Keep in mind that while Slony-I provides you with a read-only replica (able to service queries).  At present WAL log replication (in 8.2 or otherwise) would allow you to have a 'warm standby' type database - which would be somewhat in sync (pending the latest transactions), but would be unable to service queries (essentially, you'd have a server that was sitting with postmaster in a recovery state).

Chander Ganesan
Open Technology Group, Inc. - Expert PostgreSQL Training
One Copley Parkway, Suite 210
Morrisville, NC  27560
Phone: 877-258-8987/919-463-0999
http://www.otg-nc.com

The big improvement would be indeed to have the infrastructure to start
up a standby by simply pointing it to the master server, no other setup
needed. Implement that, make it reliable, and any beginner to postgres
will be able to easily set up a WAL shipping based standby. Right now
you still have to do some complicated scripting to make it work (no idea
how much 8.2 will help here, didn't try yet).

Cheers,
Csaba.




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