Quite a few databases run on raw partitions. Often the "big, old" ones. Oracle, DB2, Sybase come to mind. To improve performance, many OSes also provided ker

Quite a few databases run on raw partitions. Often the "big, old" ones. Oracle, DB2, Sybase come to mind. To improve performance, many OSes also provided kernel extensions to provide a DB-specific alternative block-device API for faster "raw" I/O and something like "async" I/O, rather than going through the regular unix block layer. These extensions were probably only ever used by databases.