Technical data

A-6 Fabric OS Administrator’s Guide
Publication Number: 53-0000518-09
Evaluating the Fabric
A
• Determine how any multipathing software will respond to a fabric service interruption
If current details about the SAN are already available, it might be possible to skip the Data Collection
step. If not, it is necessary to collect information about each device in the SAN. Any type of device
might be able to bind by PID; each device should be evaluated before attempting an online update. This
information has broad applicability, because PID-bound devices are not able to seamlessly perform in
many routine maintenance or failure scenarios.
1. Collect device, software, hardware, and configuration data.
The following is a non-comprehensive list of information to collect:
• HBA driver versions
• Fabric OS versions
• RAID array microcode versions
• SCSI bridge code versions
• JBOD drive firmware versions
• Multipathing software versions
• HBA time-out values
• Multipathing software timeout values
• Kernel timeout values
• Configuration of switch
2. Make a list of manually configurable PID drivers.
Some device drivers do not automatically bind by PID, but allow the operator to manually create a
PID binding. For example, persistent binding of PIDs to logical drives might be done in many HBA
drivers. Make a list of all devices that are configured this way. If manual PID binding is in use,
consider changing to WWN binding.
The following are some of the device types that might be manually configured to bind by PID:
• HBA drivers (persistent binding)
• RAID arrays (LUN access control)
• SCSI bridges (LUN mapping)
3. Analyze data.
After you have determined the code versions of each device on the fabric, they must be evaluated to
find out if any automatically bind by PID. It might be easiest to work with the support providers of
these devices to get this information. If this is not possible, you might need to perform empirical
testing.
Binding by PID can create management difficulties in a number of scenarios. It is recommended
that you not use drivers that bind by PID. If the current drivers do bind by PID, upgrade to WWN-
binding drivers if possible.
The drivers shipping by default with HP/UX and AIX at the time of this writing still bind by PID,
and so detailed procedures are provided for these operating systems in this chapter. Similar
procedures can be developed for other operating systems that run HBA drivers that bind by PID.
There is no inherent PID binding problem with either AIX or HP/UX. It is the HBA drivers
shipping with these operating systems that bind by PID. Both operating systems are expected to
release HBA drivers that bind by WWN, and these drivers might already be available through some
support channels. Work with the appropriate support provider to find out about driver availability.