> I need to mount a two nodes cluster with postgres as service. I have mounted > it in the past but with a shared storage and using GFS but now I don?t have > this element. > > The idea is to have a master node with all the data in its own disk and have > a mechanism to replicate this data to the slave node in its own disk. If the > master goes down the slave begin to give the service and the flow of data > will go from this node to the other one. (the slave node becomes the master > one) > > Is it possible to do something like this? To get a good HA solution it is always necessary to know all edge cases of the clients. If you can modify the clients/application it is much easier to get a working HA solution. Also you need to define what is HA? Failover in seconds? minutes? seamless? Client reconnect? With postgresql 8.3+ (i think it started with 8.3) you can do logshipping. That results in an active server accepting connections and a standby. The standby does not accept connections. It follows the original data pretty close but can lag behind (same lag goes for mysql replication, except mysql allows readonly on the slave). You need to script the failover. That is, detect that the master missbehaves, shoot it (important!) and switch the standby from replication to service. You can't have a switchback to the master. Clients need to detect that they lost connection and reconnect. This solution is straight forward, easy to understand and holds no surprises (so why did it do this? How did i loose this transaction?). Failover time depends on timeouts (how long do you wait before you decide that the master is dead?) but can be done sub-five-minutes. Starting with postgesql 9 you can have hot-standby that accepts read-only connections. And the standby can upgrade the connections to read-write without a reconnect. You still need to work your way through the ip failover. Haven't used this (and 9 is still beta). Greetings Christoph -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
