HP StorageWorks Fabric OS 5.X Administrator Guide (AA-RVHWB-TE, September 2005)

214 Configuring the PID format
• If you are running dual-fabrics with multipathing software, you can update one fabric at a time without
disrupting traffic. Move all traffic onto one fabric in the SAN and update the other fabric, and then
move the traffic onto the updated fabric, and update the final fabric.
• Without dual-fabrics, HP recommends stopping traffic. This is the case for many routine maintenance
situations, so dual-fabrics are always recommended for uptime-sensitive environments. If your fabric
contains devices that employ static PID binding, or you do not have dual-fabrics, you must schedule
downtime for the SAN to change the PID format.
You can find details on the impact of PID changes in the following publications, which are available on
the HP web site http://welcome.hp.com/country/us/en/prodserv/storage.html
.
The following sections describe various impacts of PID format changes in greater detail.
Host reboots
In some Fibre Channel SAN environments, storage devices and host servers are bound to the host
operating system by their PIDs (called their Fibre Channel addresses). In these environments, the hosts and
target HBAs in a SAN need to know the full 24-bit PIDs of the hosts and targets they are communicating
with, but they do not care how the PIDs are determined. If a storage device PID is changed, however, the
host must reestablish a new binding, which requires the host to be rebooted.
With the introduction of the 4/8 SAN Switch, 4/16 SAN Switch, SAN Switch 2/8V, SAN Switch
2/16V, SAN Switch 2/32, Brocade 4Gb SAN Switch for HP p-Class BladeSystem, and SAN Switch
4/32 and the Core Switch 2/64, SAN Director 2/128, and 4/256 SAN Director, the Native PID format
used in earlier switches was supplemented with the Core PID format, which is capable of addressing
higher port counts. Changing from Native PID format to Core PID format changes the PID, which requires
hosts that use port binding to be rebooted.
Static PID mapping errors
If possible, do not use drivers that employ static PID binding.
With the WWN or dynamic PID binding most typically used with drivers, changing the device’s PID does
not affect the PID mapping. However, before updating the PID format, it is necessary to determine whether
any devices in the SAN use static PID binding.
For those few drivers that do use static PID binding, changing the PID format breaks the mapping, which
must be fixed either by rebooting the host or by using a manual update procedure on the host.
To correct mapping errors caused by static PID binding, see the following sections:
• See ”Evaluating the fabric” on page 216 for details on finding devices that use static PID binding, and
then see ”Online update” on page 218 or ”Offline update” on page 218 for recommendations.
• See ”Converting port number to area ID” on page 222 for instructions.
Changes to configuration data
Table 45 lists various combinations of before-and-after PID formats, and indicates whether the
configuration is affected.
CAUTION: After changing the fabric PID format, if the change invalidates the configuration data (see
Table 45 to determine this), do not download old (pre-PID format change) configuration files to any switch
on the fabric.