Thats just the interface that the disk is connected to the storage processor

It has not relation to what the SP is offering to SAN clients.

You can do FC, ISCSI, FcoE with either FC, SATA or SAS disks.

The VNX only uses SAS disks – but there are two classes

Regular SAS disks with 10k/15k rpm that are faster but smaller and more expensive

And NL-SAS (nearline SAS) which are 7.2k rpm – bigger, cheaper and and slower

I would suggest to look at the VNX performance fundamentals on Powerlink

http://powerlink.emc.com/km/live1/en_US/Offering_Technical/White_Paper/h1094_Unified_Storage_Fundamentals.pdf

Rainer