SAN Boot Implementation and Best Practices Guide ... - IBM Redbooks

Draft Document for Review June 27, 2012 9:05 am SG247958-Introduction to SAN Boot-CL.fm
1.2 SAN Overview
A SAN is categorized as a high-speed network, attaching servers and storage devices. For
this reason, it is sometimes referred to as “the network behind the servers.” A SAN allows
“any-to-any” connection across the network, using I/O elements such as routers, gateways,
hubs, switches and directors.
For businesses, data access is critical and requires performance, availability, and flexibility.
In other words, there is a need for a data access network that is fast, redundant (multipath),
easy to manage, and always available. That network is a Storage Area Network (SAN).
A SAN is a high-speed network that enables the establishment of switched, routed, or direct
connections between storage devices and hosts (servers) within the specific distance
supported by the designed environment. At the basic level, the SAN is a Fibre Channel (FC)
network; however, new technology now enables this network to be routed or tunneled over
many other networks as well.
The SAN can be viewed as an extension of the storage bus concept, which enables storage
devices to be interconnected using concepts similar to that of local area networks (LANs) and
wide area networks (WANs). A SAN can be shared between servers or dedicated to one
server, or both. It can be local or extended over geographical distances.
For more information about designing SANs, visit Designing an IBM Storage Area Network,
SG24-5758
1.3 What is WWNNs and WWPNs
A WWNN is a World Wide Node Name; used to uniquely identify a device in a Storage Area
Network (SAN). Each IBM Storage device has its own unique WWNN. For example, in a
DS8000, each Storage Facility Image (SFI) has a unique WWNN. For SVC, each SVC Node
has a unique WWNN.
A WWPN is a World Wide Port Name; a unique identifier for each Fibre Channel port
presented to a Storage Area Network (SAN). Each port on an IBM Storage Device has a
unique and persistent WWPN.
IBM System Storage devices use persistent WWPN. This means if an HBA (Host Bus
Adapter) in an IBM System Storage Device gets replaced, the new HBA will present the same
WWPN as the old HBA. IBM Storage uses a methodology whereby each WWPN is a child of
the WWNN. This means that if you know the WWPN of a port, you can easily match it to the
WWNN of the storage device that owns that port.
A WWPN is always 16 hexadecimal characters long. This is actually 8 bytes. Three of these
bytes are used for the vendor ID. The position of vendor ID within the WWPN varies based on
the format ID of the WWPN. To determine more information we actually use the first character
of the WWPN to see which format it is (the vendor ID position is bold):
1 = IEEE 803.2 standard format (example 10:00:00:00:c9:2f:65:d6). This is an Emulex HBA
WWPN since Emulex owns the 0000c9 company ID.
2 = IEEE 803.2 extended format (example: 21:00:00:e0:8b:90:90:04). This is a Qlogic HBA
WWPN since Qlogic owns the 00e08b company ID.
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