On 24/09/10 13:57, Simon Riggs wrote:
If you want high availability you need N+1 redundancy. If you want a standby server that is N=1. If you want a highly available standby configuration then N+1 = 2.
Yep. Synchronous replication with one standby gives you zero data loss. When you add a 2nd standby as you described, then you have a reasonable level of high availability as well, as you can continue processing transactions in the master even if one slave dies.
Show me the textbook that describes what happens with 2 standbys. If one exists, I'm certain it would agree with my analysis.
I don't disagree with your analysis about multiple standbys and high availability. What I'm saying is that in a two standby situation, if you're willing to continue operation as usual in the master even if the standby is down, you're not doing synchronous replication. Extending that to a two standby situation, my claim is that if you're willing to continue operation as usual in the master when both standbys are down, you're not doing synchronous replication.
-- 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
