If you need to create a file of a certain size and the file contents don’t matter, you can use the Fsutil command as follows
fsutil file createnew <filename> <filesize in byte>
For example,
fsutil file createnew d:\temp\1mbfile.txt 1000000
creates a 1MB file named 1mbfile.txt in the d:\temp folder. I used this command to create files of different sizes to make some local network speed test
