The easiest way to find raw hard drive performance is using hdparm, which we describe in Section 4.3.1.2. But this is raw hard drive performance, not taking into account things like overhead from the filesystem or write performance.
The other application you can use to test how the filesystem works, or for devices that do not work with hdparm is to use dd. The dd command is used to write or read data and perform some conversion along the way. The nice part of the command for us is that it can create a file of any size containing ASCII NULL (0), which allows us to test consistently. Since the data we want to write is being generated in the CPU and memory which is always faster than the hard drive, this gives a good look at the disk bottleneck.
This is used in conjunction with time which gives the amount of CPU, system, and user (real) time used to run a particular command. You can then divide out the size of the file created by the number of user seconds to run the command to get a Mbps rating.