I have already set up jumbo frames on ESX and open-e, which lead to a speed increase of about 5 MiB/s.

At the moment i am using a single connection. I plan to use MPIO in the future, but i would first like to have everything running at a reasonable speed for a single gigabit ethernet connection.

As the theoretical maximum for GBe is 125 MiB/s, i think i should at least achive ~100 MiB/s, especiallly at my test setup using a cross link cable.

Are there any common problems/pitfalls i have to know about?

I am also unsure about the testing with IOmeter. Sometimes the transfer rate starts at about 12 Mib/s and, within a minute, climbs up to approx 50 Mib/s. Is this behavious expected or perhabs a sign of problems?