On 21/06/10 00:34, Elior Soliman wrote: > Hello, > > My company looking for some solution for High availability with Postgres. > > Our optional solution is as follows : > Two DB servers will be using a common external storage (with raid). Both > servers are going to use the same DB files on the storage (as > active/passive) Why do you want that configuration? For PostgreSQL, a warm standby setup using WAL-based replication (PITR, or "point in time replication") is usually the preferred approach. There are also add-on replication solutions like bucardo and slony-I. > Now I'm trying to understand how Postgres can work with thi > configuration. I.e : > > DB_server1 crashed, so we want to start DB_server2 using same files. > Is it possible ? Depending on why and how db_server1 crashed, it may be. If the DB server crashed in such a way as that it didn't stomp all over the shared storage, then you can unplug db_server1 from the shared storage or otherwise render that shared storage completely inaccessible by db_server1, then start the database on db_server2. If you fail to render it inaccessible by db_server1 or make sure db_server1 is stone dead (powered off) first, you may land up with two postmasters trying to work with the same data. This *will* cause corruption if you override/bypass Pg's attempts to detect and prevent this fault condition. The only time you can really use shared storage is if you have a heartbeat setup with STONITH. Even then, I'd personally prefer to use network replication if at all possible, since it removes the shared storage as a central point of failure. It also lets you use much, much faster locally attached storage where disks are dedicated to PostgreSQL. -- Craig Ringer -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
