Here's a sample config of VSF stacking using a pair of 2930F switches.
More details about VSF are in the manual and there's another post about VSF here
I'm using a total of 4 ports at 1Gb each. Three of the links are fiber/SFP's and the 4th link is a copper port. You can mix and match. I had a spare ethernet between closets and we ran a multi-pair fiber between the closets. If the fiber gets damaged by a contractor working in the building, the copper port will take over. Once the construction is all done, I'll probaly remove the copper connection, but for now this is what we have. As Matthew_Fern said, the speed must match.
hostname "MyVirtualSwitchStack-VSF"
vsf
enable domain 5
member 1
type "JL256A" mac-address 123456-789abc
priority 128
link 1 1/48,1/50-1/52
link 1 name "I-Link1_1"
link 2 name "I-Link1_2"
exit
member 2
type "JL256A" mac-address 123456-789abd
priority 120
link 1 2/48,2/50-2/52
link 1 name "I-Link2_1"
link 2 name "I-Link2_2"
exit
port-speed 1g
exit
We're using old cisco SFPs for this, so I had to enable the:
allow-unsupported-transceiver
to get them to work, but if you're using HP SFP, you dont need that line.