Netbackup appliance 5230 & Fibre Channel Autonegotiation
In my experience and, as far as I know, the best practice from vendors of OEM equipment (e.g. HP) is to always set fixed speed on SAN switch ports. I have personally never left a SAN switch port in auto-negotiate mode. It's just something that we learnt, long ago, to not do.
It's better to have fixed speed and to enable monitoring of port errors, than it is to leave a port to negotiate downwards in speed. Both ends can then concentrate on data traffic handling rather than spending time and traffic negotiating speeds. And you get to nip problems in the bud sooner, because more errors will be detected sooner.
One of the best tests is to simply check the light signal / power levels. Any signal loss greater than -12dB on a standard server to switch connection really should be investigated and rectified. SANs should on the whole be really very very clean indeed, with the only known signal loss events being server reboots. Flapping up/down ports can be quite disruptive. More best practice is to persitently disable known unused ports - and only re-enable them when zoning/adding new cabling/patching and connectivity.
