HP StorageWorks MSA 2.8 SAN Switch - Manual (Page 194)

Troubleshooting
194 Fabric OS Procedures Version 3.1.x/4.1.x User Guide
About Troubleshooting
Troubleshooting should begin at the center of the SAN — the fabric. Because
switches are located between the hosts and storage devices, and have visibility
into both sides of the storage network; starting with them can help narrow the
search path. After eliminating the possibility of a fault within the fabric, see if the
problem is on the storage side or the host side, and continue a more detailed
diagnosis from there. Using this approach can quickly pinpoint and isolate
problems.
For example, if a host cannot see a storage device, run a switch command to see if
the storage device is logically connected to the switch. If not, focus first on the
storage side. Use storage diagnostic tools to better understand why it is not visible
to the switch. Once the storage can be seen from the switch, if the host still cannot
see the storage device, then there is still a problem between the host and the
switch.