Optimal Jumbo Frame size?

All your devices support it, but to what packet size do they support? The standard is 9K, but some devices differ from that.

Thanks, I'll check everything for 9K.
Curious to see how my Iometer results will change once I enable JF.

Depends on the device. I've seen some cheap PC motherboard onboard NIC drivers that make things worse with Jumbo on.

'Luckily' my MOBO onboard Realtek NIC failed a while back so I am now using an Intel Pro 1000 NIC instead.

Oh oh!
I enabled jumbo frames on everything (PC NIC, notebook NIC, ReadyNAS, HP switch) but now I cannot access my ReadyNAS.
RAIDar finds it, but when I click on connect Firefox never opens the ReadyNAS page.
Also, my Squeezbox SB3 on my desk continually cycles through showing the date and time (paused) and "Can't connect to server".
I just Googled my router and determined that is NOT in fact jumbo frames compatible. D'Oh!

How do I regain contact to my Pro to disable jumbo frames?

Have you also set your other NIC on your Pro to JF? If not you should be able to regain access by simply unplugging the first NIC and plugging into the second.

As far as determining what your maximum packet size is you can ping your devices and set the 'do not fragment' flag (-f) and use different sized packets (-l xxxx), starting with a lower number (1472 perhaps?) until you recieve "Packet needs to be fragmented but DF set" indicating the packet is too big to traverse your network without fragmentation.

IE

ping your_NAS -f -l 1472

I am running my Pro NICs teamed, 802.3ad LACP Layer 2 to two trunked ports on my HP 1810G-24 switch.

Originally I though it was my routers lack of JF support that was causing the issue.
So I unplugged the router from my switch and still could not get to Frontview.
RAIDar could find it, just no Frontview via Firefox or IE.

Are JF not compatible with teamed NICs on the Pro?

I was only able to regain access to my NAS by reinstalling the OS.
Now no issues with NICs teamed (as above) and JF not enabled.

Also, when JF were enabled on the NAS, my Squeezebox devices kept losing their network connections (the displays would randomly show not network connectivity). Is SqueezeCenter compatible with JF?

SqueezeBox is probably not JF compatible.

I'll buy that.

What about JF and teamed NICs on the Pro?