All WWNs are registered with and assigned by the The Institute of Electrical and Electronics Engineers (IEEE). This is done to assure each and every WWN is unique. A WWN is similar in concept to a network card's MAC address in an IP network, but is formatted differently.
WWNs are formatted as follows:
WWN= XYYYYYYZ ZZZZZZZZ (Example: 500060E8064183F3)
X = the first 4-bit field, called the NNA, specifies the format the WWN follows. This number is a "5" for storage target ports, and either a "1" or a "2" for an HBA port.
YYYYYY = called the organizational unique identifier (OUI) which is assigned by the IEEE to specific vendors (Such as Qlogic, Emulex, Hitachi, EMC, IBM, etc...) This is why the address in this area always seems to be similar if you are buying from a specific vendor.
ZZZZZZZZZ = the vendor specified identifier (VSI), which is defined by the vendor owning the OUI. These numbers can be changed by the vendor to develop an offset of the node WWN to get a port WWN. As an example, an HBA may have dual ports. The HBA is assigned a node WWN, and an offset is used to get the port WWN for each port on the HBA by changing the value of the VSID.
Dig Deeper on SAN technology and arrays
Related Q&A from Christopher Poelker
SAN expert Chris Poelker compares connecting a SAN with wavelength cabling and dark fiber and discusses the pros and cons of each. Continue Reading
SAN expert Chris Poelker discusses how to change the size of a LUN in a Microsoft cluster server environment. Continue Reading
Storage expert Chris Poelker discusses SATA/SCSI compatibility issues in this expert advice article. Continue Reading