SQL Server database management systems typically make use of three different files. There is one .mdf file, or primary data file for each database. Views, tables and other objects must be stored in the .mdf file. While a database can function with only a .mdf files it is common for secondary data to be stored in a .ndf file. If a database exceeds the maximum for a single Windows file, additional data can be stored in a .ndf file. Relativity stores full text indexes in .ndf files.

There can be multiple .ldf, or log files for each database. Log files record the time of transactions in the SQL database and can be use for recovery when there is a database.

kCura recommends that these files be kept on separate disks.