Starting with SQL Server 2008, SQLIOSim is included with the SQL Server product installation. SQLIOSim simulates tests of read, write, checkpoint, backup, sort, read-ahead activities on SQL Server. SQLIOSim is not a benchmark tool or a utility to determine I/O capacity of storage system. For test I/O capacity you should use SQLIO. SQLIOSim replaces the SQLIOStress utility, formerly known as SQL70IOStress.
The SQLIOSim utility has 2 executable files, SQLIOSim.com (command-line tool) and SQLIOSim.exe (GUI application). Both executable files provide identical simulation capabilities, and it really depends on what version you are most comfortable with as to which version you should use.
Using these utilities, you configure the server how you would configure SQL Server, and it provides statistics on drive performance.
You do not need to have SQL Server installed to run the utilities, and you do not want to use any SQL Server database files to run the tests. The utility will create all the files it needs to conduct your tests, using the mdx and idx file extensions.
The output helps you identify drive-related issues.