HP AA-RS2WC-TE, Installation Manual

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Technical Specifications
184 Core Switch 2/64 V4.1 Installation Guide
Extensive Information on the PID Format
This section provides best practices for updating an existing production SAN to
the new PID format. In addition to the core PID format update process, there are a
number of very common scenarios in which a device may be assigned a new PID.
Therefore the procedures included in this section are applicable to other areas of
SAN administration, and should be generally useful to any SAN administrator.
A Port Identifier (PID) is one of two addressing mechanisms used in Fibre
Channel. This is analogous to specifying the physical switch and port a device is
attached to in data networks. It is not analogous to an IP address. There are
numerous situations in which a device's PID may change. PIDs are assigned by a
Fibre Channel switch when a device logs into the fabric. For example, a PID
would be:
011F00
The other Fibre Channel addressing mechanism is the World Wide Name
(WWN).
This is analogous to an Ethernet MAC address. A device's WWN never changes.
WWNs are assigned by the factory when a device is manufactured, as shown in
the following example:
10:00:00:60:69:51:0e:8b
The method switches use for assigning PIDs has changed between the 16-port
switches and the larger port count products. The old PID format was XX1YZZ, Y
was a hexadecimal number which specified a particular port on a switch and 1 was
a constant.
(The use of the constant was based on an overly conservative reading of the Fibre
Channel standards.) XX was used for the domain ID and ZZ for the AL_PA. Since
all switches had sixteen or fewer ports at the time that method was established,
one hexadecimal digit was entirely adequate.
The new format is XXYYZZ. YY represents a port.Using the entire middle byte for
the port allows addressing up to 256 ports per switch. This change was necessary
to support products with more than sixteen ports. When a switch with the new
core PID format is introduced into an existing fabric, the core PID format needs to
be set on all switches in the fabric to prevent segmentation.
To make this change, it is necessary to schedule an outage for the fabric. This does
not require application downtime, if redundant fabrics are used. If redundant
fabrics are not used, there are numerous failure cases and even routine
maintenance scenarios which result in application downtime. This is true for any
currently available Fibre Channel technology.