On Sat, 2011-01-01 at 14:40 -0800, Josh Berkus wrote: > Standby in general deals with the A,D,R triangle (Availability, > Durability, Response time). "Any one" configuration is the A,R > configuration, and the only reason to go out with it for 9.1 is > because it's simpler to implement than the D,R configuration (all > standbys must ack).
Nicely put. Not the "only reason" though... As I showed earlier, the AR gives you 99.999% availability and the DR gives you 94% availability, considering a 3 server config. If you add more servers, the availability of the DR option gets much worse, very quickly. The performance of AR is much better also, and stays same or better as cluster size increases. DR choice makes performance degrade as cluster size increases, since it works at the speed of the slowest node. The fact that I can get "5 Nines" with simpler code makes it even sweeter. quorum commit > 1 can improve the durability guarantee of data, but it also seems that many people wouldn't understand its implications and would mis-configure it, to our collective embarrassment. -- Simon Riggs http://www.2ndQuadrant.com/books/ PostgreSQL Development, 24x7 Support, Training and Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
