Chapter 3 Configuring Your LibraryWorking With FC I/O BladesScalar i500 User’s Guide 117map the controller device to a different LUN if an application typicallyexpects to see a media changer device (partition) or tape drive at LUN 0.LUNs can also be mapped to be accessible by specific host server WorldWide Port Name (WWPN). Mapping a LUN to a specific WWPN can beused instead of channel zoning to control device visibility. Mapping aLUN to more than one WWPN may be useful for creating redundantpaths to a media changer device (partition), tape drive, or controllerdevice. LUNs will need to be mapped to each WWPN for host serversthat use multiple ports (e.g., multi-ported HBAs or multiple HBAs) ifaccess is desired via all the host server ports (e.g., a LUN would need tobe mapped to both WWPNs of a server that uses a dual-port HBA).LUN masking is a complementary concept to host mapping in that LUNsthat are mapped to specific host server WWPNs are hidden (i.e., masked)from other host servers. This is useful when more than one host server isattached to the FC I/O blade (e.g., in a SAN). One or more of the LUNscan be masked from discovery by specific host servers while maintainingtheir mapping and accessibility to other host servers via the same port(s).Host Mapping Vs.Channel Zoning 3 Channel zoning places an operational restriction on mapped LUNs (forexample, if port 1 is zoned to ports 3 and 4, but LUNs from ports 3through 6 have been mapped to a specific host server WWPN, the deviceson ports 5 and 6 cannot be accessed from that host via port 1, even thoughthey are mapped to it; only the devices on ports 3 and 4 would beaccessible from the host via port 1).Host mapping can be used to control visibility of the media changerdevices (partitions) found on the FC I/O blade internal virtual port, whilechannel zoning can be used to create simple access control to the othertarget devices. If the host mapping capabilities are used to controlvisibility and access for all the LUNs, channel zoning might not benecessary or desired.Note: On the operator panel, the host mapping screens (Setup > FCI/O Blades > Host Mapping) are not available unless FC hostmapping is enabled. See Enabling/Disabling FC HostMapping on page 113.
