I have a Cisco Catalyst 100mbps switch between my source and destination workstations. I'm trying to copy about 26.1GB across and it's going to take circa 40minutes.

My question is: Why am I only getting 11.2MB/s when I have a 100mbps switch?

Quoting here I get an answer

How are you measuring, and are you keeping in mind the difference between MB and Mb?

10 MB/s would be near the maximum speed of a 100 Mb/s network.

Exactly. 100Mb/8 = 12.5MB/s in a perfect environment. Skim a little off the top for overhead and you don't seem like you're in bad shape.