Application programs such as database management systems frequently avoid the file management of the UNIX system and the data is written directly to a partition. In this case, the partition is used as a raw device. No file system exists in such a partition. Using this type of storage might bring certain advantages regarding the speed when accessing the data, but requires its own file management.

An Oracle database can be operated from raw devices. The SAP utilities for backing up the database support this configuration.

Working with raw devices brings considerable performance gains for the following reasons:

• Since the usual buffer cache for a file system is not needed, less main memory is required.

• You do not have to administer a file system.

• Since no management information has to be stored on the disk, less disk space is required.

• Since the accesses do not have to be synchronized and the management information does not have to be recorded, the load on the CPU is reduced.

Working with raw devices makes administration more difficult for the following reasons:

• There is no description of the files residing on the raw devices in the system.

• The configuration of the storage space is inflexible because only one database file is permitted for each raw device (and therefore for each partition). The sizes of the individual partitions must be adjusted to the sizes of the database files. This makes later relocation of the database files to other partitions more difficult.