I'm in the process of building out a ZFS file server for three XenServer Hypervisors.
This is in one of the HP Prolait G6 2U chassis with 25*2.5 SAS bays sitting in the front. (2*L5520's + 48GB memory)
These all are hooked up to an LSI HBA (not sure of the model, it's one of 'em that plays nice...