Hi,
Clusters basicaly can be set up by two ways: active/passive and active/active.
Active/Passive means that one server works, and the others stay waiting the active one fails.
On Active/Active, both servers are up, running, and working like one.
Samba supports both of them. Active/Passive with many tools and ways, and Active/Active with CTDB.
But on your case, I suggest that: first, you buy a really big storage, that can be stacked. If you are looking for a HA, you must buy two storages, with redundant features.
Then, you install two servers, connected to the storages, with samba+ctdb. That you provides HA, one IP to user's access, possible to grow up with modularity.
Otherwise, the storage capacity of normal servers appears to be small to that case, and you will must split the data into all those servers: more data, more servers.
[]'s
Rafa
Linux, Linux and Linux!
Suporte Linux