jumbo frames. Powerconnect 5424

Hi

I have some interoperability problem between pc5424 and extreme networks. I have connected few pc 5424  via trunk port 802.1q to black diamond 8k.

I see some packet loss, about 1% on nfs. When i flood via icmp, 1000 pkt/s, the loss is about 5 packets. Of course bigger problem for me is nfs..

All switches work in L2 only, i don't see any options for jumbo on pc5424,  what is size  of ethernet jumbo frame ?

On extreme switch i have: Jumbo: Enabled, MTU= 9216,

All servers have:

ipmtu: 1500
size jumbo frames: 9000

When i connected only two pc5424 everything works ok..

someone had similar problem ? thanks You for some advice

greetings

Peter