During Health Checks I check the file transfer speed between the BizTalk servers and the SQL server. To do that, I copy a 100 MB file from the BizTalk servers to the SQL server. Even though this is not an exact science, it gives a good indication about the network and disk speed.
I normally do not carry a 100 MB test file with me. Luckily it is easy enough to create one by using FSUTIL:
FSUTIL FILE CREATENEW 100MBTest.file 104857600