I want to measure the network speed between two PCs on Local Area Network. (I'm thinking of getting a Network Area Storage (NAS) device and I want to see how fast the current setup is to get an idea of how fast the NAS needs to be.
I'm thinking I'll just copy some files and look at how long that takes, but I thought there might be a more precise way to measure that.
This might work if you do the same process with another computer. It might not be precise, but could give an idea.
Each NAS device tends to produce as part of its spec a throughput number. Generally speaking if speed is of concern, you would be better off which choosing SAN over NAS.
To measure the network performance, iperf is the best tool I have seen.
I do not believe this will be helpful in solving your problem, however. You aren't going to be able to size a NAS solution based on the network performance.
Transferring a file using the same protocol the NAS would is certainly more relevant for this case. Still, not helpful.
You can assume that any modern machine can transfer data at over 90% of the link speed. (whether involving the local storage or not, unless there's a problem or significant other load).
A dozen reasonably modern clients should be able to crush a fairly powerful NAS. You really need to simulate real-world load. That's basically imposssible.
You need to approach sizing your NAS solution from a different perspective. The capabilities of the clients really aren't relevant.