You can get close to Robocopy speed with a simple C # program that does asynchronous reads and writes using the standard FileStream with a 64 KB buffer. Large buffer sizes up to 256 KB will give a slight increase in performance. The larger 256K, the slower they will slow down. In my tests, using a 512K buffer took almost twice as much time as copying with a 256K buffer.
The idea is pretty simple:
Read the first buffer from the source file do { start asynchronous write to destination file. Read the next buffer from the source file wait for asynchronous write to complete } while not end of file
This is a pretty simple thing to write. My program, which does this almost as fast as Robocopy, and does not cause the types of problems that Robocopy causes when you copy a very large (one hundred gigabytes) from the server.
A bit more information about the problem with a large copy of the files.
Please note that this asynchronous read / write function does not greatly affect performance if you read and write to the same physical disk. This is most effective when the source and destination are on different drives.