Hi Vanessa,

> that garantize my service always available.

nope, impossible. "always" is a very strict term.

Just to give you a starting point, you might go the following route:

- set up a two-node HAE cluster using SLES11 + HAE
- define an IPAddr2 resource for the IP address of the clustered
- define an Apache2 resource
- add an order constraint (Apache requires IP)
- add a location constraint (Apache requires IP on the same node)
- configure your Apaches on the nodes
- start heartbeat

There can (and most probably will) be tons of other configuration adaptions necessary:
* fencing on a two-node cluster needs special care (what if both nodes start the resources, esp. the IP address?)
* you might get away with switching only the IP address, depending on your IP stack setup on the nodes (by running Apache constantly you'll have quicker fail-overs, but Apache might need the desired IP address visible on the node to start up properly and bind to that IP)
* you still have a possible SPOF (NAS) or two... (network between NAS and servers, between servers and clients, power, ...)

Seems I misplaced my "building a complete cluster in 5 steps" book but in the combination of manuals and all those implementation notes out there, you ought to find your way. And we'll be here for specific question.

Just keep in mind: HA is a design principle, not something you set up by installing two servers. That'd be like trying to win a Formula 1 race with one of those British kit cars... but those Brits will take you from A to B rather stylishly, so if that's what you need, why not go for it?