InfiniBand merges both storage area networks and system area networks and gets the bus out of the way. There may be redundant paths through the fabric to promote fault tolerance, and multiple InfiniBand subnets can be connected via InfiniBand routers.
Hosts can have multiple HCAs.
The PCI bus in a node can still be used for local disks, SCSI controllers, LAN interfaces, video cards and the like, without affecting the performance of the InfiniBand network. Initial rollout of InfiniBand will be a stopgap, with the HCA being a PCI-X card. The development of direct HCA-memory controller connections will take place over the next two years. System designers will have the option of connecting almost any type of device, even an Ethernet NIC, via the local system bus or via InfiniBand. Devices integrate TCAs, letting them connect to InfiniBand switches.