Specifications

utility. This might comprise many storage devices, including disk, tape, and optical
storage. You can locate the storage utility far from the servers that use it.
Think of ESCON as the first real SAN. It provides connectivity that is commonly
found in SANs. However, it is restricted to ESCON hosts and devices.
Fibre-channel SANs, however, provide the capability to interconnect open systems
and storage in the same network as S/390 and zSeries host systems and storage.
This is possible because you can map the protocols for attaching open systems and
S/390 and zSeries host systems to the FC-4 layer of the fibre-channel architecture.
18 ESS Host Systems Attachment Guide