HP StorageWorks 2/16V HP StorageWorks Fabric OS 5.X Procedures User Guide (AA- - Page 214

• 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. 214 Configuring the PID format