 <p>The Microsoft trained and best practice methodology is as follows:</p> <ul> <li>Log files are placed on a separate physical drive</li> <li>Data files are placed on a separate physical drive</li> <li>Multiple file groups: When a particular table is extremely big. Often the case in transactional database (Separate Physical Drive) </li> <li>Multiple file groups: When using ranges or when wanting to split lookup data into a read-only database file (Separate Physical Drive)</li> </ul> <p>Keep in mind that an MDF technically works similarly to a hard drive partition when it comes to storing data. The MDF is a randomly read file, whereas the LDF is a sequentially read file. Therefore splitting them into separate drives causes a huge performance gain, unless running solid state drives, in which case the gain is still there.</p>