Recommendations; New Fabrics; Existing Fabrics - HP StorageWorks MSA 2/8 - SAN Switch User Manual

Recommendations

Redundant fabrics and multi-pathing software are recommended for
uptime-sensitive environments. If redundant fabrics are not used, there are
numerous possible failure cases and even routine maintenance scenarios that can
result in application downtime. This is true for any currently available Fibre
Channel technology.
Examples of scenarios protected by redundant fabrics include:

New Fabrics

For new fabrics, the PID format should always be set to the larger port count
addressing method before the fabric enters production. When updating an existing
SAN, there are several scenarios which must be evaluated before changing the
PID format.
Proactively setting the core PID format on new fabrics is strongly recommended
to save potential administrative effort later on. There is no difference in the
behavior of a fabric with either PID format.
Core PID is enabled by default on 4.x switches (Core Switch 2/64 or SAN Switch
2/32). Use the configure command to enable Core PID on 2.x and 3.x switches
before mixing with a 4.x switch fabric.

Existing Fabrics

When a switch with the larger port count format is introduced into an existing
fabric, the core PID format must be set on all switches in the fabric to prevent
segmentation. This does not require application downtime if redundant fabrics are
used. If redundant fabrics are not in use, it is necessary to schedule an outage for
the fabric.
Fabric OS Procedures Version 3.1.x/4.1.x User Guide
Add/move/change operations for devices or switches
Major upgrades/changes to fabric architecture
Physical disasters
Changing the Core PID format
Changing any other fabric-wide parameters, for example ED_TOV
Erroneous zoning changes/user error
Updating Switches to the Core PID Addressing
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