Technical data

Fabric OS Administrator’s Guide A-7
Publication Number: 53-0000518-09
Planning the Update Procedure
A
It is also important to understand how multipathing software reacts when one of the two fabrics is
taken offline. If the time-outs are set correctly, the failover between fabrics should be transparent to
the users.
You should use the multipathing software to manually fail a path before starting maintenance on
that fabric.
4. Perform empirical testing.
Empirical testing might be required for some devices, to determine whether they bind by PID. If
you are not sure about a device, work with the support provider to create a test environment.
Create as close a match as practical between the test environment and the production environment,
and perform an update using the procedure in “Online Update” on page A-8.
Devices that bind by PID are unable to adapt to the new format, and one of three approaches must
be taken with them:
• A plan can be created for working around the device driver’s limitations in such a way as to
allow an online update. See the Detailed Procedures section for examples of how this could be
done.
• The device can be upgraded to drivers that do not bind by PID.
• Downtime can be scheduled to reset the device during the core PID update process, which
generally allows the mapping to be rebuilt.
If either of the first two options are used, the procedures should again be validated in the test
environment.
Determine the behavior of multipathing software, including but not limited to:
• HBA time-out values
• Multipathing software time-out values
• Kernel time-out values
Planning the Update Procedure
Whether it is best to perform an offline or online update depends on the uptime requirements of the site.
• An offline update that all devices attached to the fabric be offline.
• With careful planning, it should be safe to update the core PID format parameter in a live,
production environment. This requires dual fabrics with multipathing software. Avoid running
backups during the update process, as tape drives tend to be very sensitive to I/O interruption. The
online update process is only intended for use only in uptime-critical dual-fabric environments,
with multipathing software (high-uptime environments should always use a redundant fabric SAN
architecture). Schedule a time for the update when the least critical traffic is running.
All switches running any version of Fabric OS 3.1.2 and later or 4.2.0 and later are shipped with the
Core Switch PID Format enabled, so it is not necessary to perform the PID format change on these
switches.
Migrating from manual PID binding (such as persistent binding on an HBA) to manual WWN binding
and upgrading drivers to versions that do not bind by PID can often be done before setting the core PID
format. This reduces the number of variables in the update process.