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Technical Specifications
idea to avoid running backups during the update process, as tape drives tend to be
very sensitive to I/O interruption. Backup all data with verification, then update
one fabric at a time, verifying I/O at each step in the process.
Offline Update
It is possible to execute an offline update with less advance planning. However, it
requires that all devices attached to the fabric be offline.
Which option to choose depends on the uptime requirements of the site. High
uptime sites should all have dual fabrics with multi-pathing software, so the
online update is an option for those SANs. Single fabric sites must use offline
procedures.
Create an update plan. Guidelines are provided above. Schedule an outage for all
devices attached to the SAN. Backup all data with verification, then update all
fabrics in the SAN at the same time. Bring all devices back online, and verify I/O.
Hybrid Update
It is possible to combine the online and offline methods for fabrics where only a
few devices bind by PID. Since any hybrid procedure will be extremely
customized, it is necessary to work closely with the SAN service provider in these
cases.
PID Frequently Asked Questions
Q: What is a PID?
A: A PID is a Port Identifier. PIDs are used by the routing and zoning services in
Fibre Channel fabrics to identify ports in the network. They are not used to
uniquely identify a device; the World Wide Name (WWN) does that.
Q: What situations can cause a PID to change?
A: Many scenarios cause a device to receive a new PID. For example, unplugging
the device from one port and plugging it into a different port will cause this. (This
might happen when cabling around a bad port, or when moving equipment
around.) Another example is changing the domain ID of a switch, which might be
necessary when merging fabrics, or changing compatibility mode settings.
Q: Why do some devices handle a PID change well, and some poorly?
A: Some older device drivers behave as if a PID uniquely identifies a device.
These device drivers should be updated if possible to use WWN binding instead.
A device's WWN never changes, unlike its PID. PID binding creates problems in
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Core Switch 2/64 V4.1 Installation Guide
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