How can I test the read speed of a RAID1 device?

Some RAID controllers speed-up read access when using RAID1. Other controllers can't do that.

Trying some RAID1 configurations, I want to know if the read speed is faster both on a single file and on several files.

There are plenty of tools which test the read/write speed of a hard drive. What about testing a RAID speed, including software RAID? Are there any tools for Windows which can do it?

There are a couple of utilities out there, you don't say what OS so here are a few:

bonnie (Linux)
HD Tune (Windows)
Intel IOMeter (Windows & Linux)

Also the tools that test a single hard drive will work just as well against a raid volume.