LUNz

LUNz is created when a host has connectivity to an array, but no LUNs have been assigned to it. This allows the host to see the array and make use of a very limited set of SCSI commands. There are more or less technical explanations.

You can see if you have a LUNz device by looking for "Z" items in /proc/scsi/scsi. The last two entries below are LUNz's:

$ cat /proc/scsi/scsi
Attached devices:
...
Host: scsi1 Channel: 00 Id: 01 Lun: 00
Vendor: DGC Model: RAID 5 Rev: 0324
Type: Direct-Access ANSI SCSI revision: 04

Host: scsi1 Channel: 00 Id: 02 Lun: 00
Vendor: DGC Model: LUNZ Rev: 0324
Type: Direct-Access ANSI SCSI revision: 04

Host: scsi1 Channel: 00 Id: 03 Lun: 00
Vendor: DGC Model: LUNZ Rev: 0324
Type: Direct-Access ANSI SCSI revision: 04
...
$ 

If you've connected a host to a second SAN but haven't assigned any real LUNs to it then an SP Collect will show you port number of the Second SAN's Service Processor which is most likely a LUNz.

It's been reported that there can be blocked I/O to EMC CLARiiON LUNz paths.

You can get rid of a LUNz by removing the zone that connects your host to the particular SAN with the LUNz OR you could add a "real" LUN to that SAN. You'll then want to reload the HBA module since it allows the kernel to see the the SCSI bus in it's final state. Rebooting is recommended to be on the safe side.