Activating the jumbo frames kills the network performance (from 30% to 15)

Hi,

I have an SSAS 2008 R2 server and an SQL Server 2008R2 on 2 servers.

with only 1 Gbps network card.

I activate the jumbo frames to see if there is an improvment on the network transfer between the 2 servers, as the current traffic is slow.

the jumbo frames works fine, a file copy operation demonstrate 50% better throughput.

From 50% to 75% of the bandwidth consumed.

but when I process my cube, the speed which was 30% before drop to 1%!!!!

so the jumbo frames killed the traffic here!

any idea why?