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some time ago a friend showed me his concept of a virtualized web application:

  • 2 Apaches - load-balanced via IPVS/LVS
  • 2 MySQL - HA via DRBD and Heartbeat

The virtualized machines all run under the same hypervisor on the same host. So I was wondering if this setup is reasonable because I see no advantage.

  • Host is SPOF
  • Load-Balancing via IPVS? Host CPU is the bottleneck anyway or can 2 virtualized CPUs handle more interrupts than the Host CPU alone?
  • MySQL HA? Isn't it faster for the hypervisor restarting a crashed guest than failover via DRBD etc...?

I don't see any advantage in network load-balancing under the same hypervisor since network I/O between guests is mapped memory anyways and therefore fast.

Any ideas, suggestions?

For me it is just overhead and single, beefier guests make more sense...

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Unless you have an imminent migration to more hosts or very odd isolation requirements (like 2 sets of completely seperate human administrators), I see little use to this scenario. –  Joris Sep 8 '10 at 8:20

3 Answers 3

Agreed on every point. If you had a hypervisor cluster, then it might have made sense, especially with a policy to always keep the guests on different hosts

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Like dyasny already said, the scenario does not make sense at all unless there's a hypervisor cluster. For a single host that kind of hoopla is just plain stupid.

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I think this configuration is only for testing and learning purpose.

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