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Re: [Linux-cluster] Cluster Planning



Scott Kellogg wrote:



Also to use an active-active (same service active on both servers) configuration + loadbalancing you will need more than 2 servers; at least 4 servers, 2 for loadbalancing (1 active/1 backup) and 2 for the critical service active concurently on both servers (no high availability, no failover).

You seem to be referring to LVS. Right, I can't implement that since I don't have enough hardware. I think that active-passive will be the way to go. When the active node dies, the passive node will take over. The data will only be as fresh as the last synchronization. That begs the question of what happens when the active node comes back up ... will the passive node (now active) sync its data to the new active node? This is where picking a synchronization method becomes vital.


That's where GFS comes in.

I don't want to sound rude, but either you (or your customer) have the budget for a cluster or not. If you don't have the budget, it's better to just use the 2nd server as hot-spare and rsync the data over to the 2nd one and do the failover by hand (and even more so the re-activation of the primary server) Or you should have bought a more expensive, more reliable server instead of two low-end ones. You *can* have low-end servers, but you need a reliable storage-infrastructure (which will be a SAN in 7 out of 10 cases and iSCSI in the other), which has a big upfront-cost.

This always reminds me of people who want to drive cars they cannot really afford. It's better to acknowledge that and accommodate to a cheaper car than sitting there one day without the money to have it repaired....



cheers,
Rainer




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