RAW devices are also supported by Oracle. With RAW devices, Oracle does not use a filesystem. The Oracle RDBMS manages the storage entirely itself. RAW devices have been very popular for Oracle because of performance. By bypassing the filesystem code, CPU usage can be reduced since there is no filesystem processing being done. However, managing Oracle on RAW devices can be complex and difficult.
Until the introduction of OCFS, Oracle RAC databases were required to be built
on RAW devices.
By using RAW devices, Oracle is responsible for the data storage, and since the Oracle RAC cluster manages the storage as well as the cluster, the system coordination problems are solved. RAW devices are limited and difficult to manage. With Oracle 10g we now have several options for a RAC cluster: RAW devices, OCFS, or ASM.