For performance reasons, each of the different types of
devspace should be stored on a different disk. At the very least, data devspaces and log-devspaces should be stored on different disks. Because all changes to the database instance are logged in the log areas , it is the log devspaces for a database instance that see the most write activity.When RAID-5 systems are used, the database instance should be configured with several data devspaces. Performance will be better with many data devspaces than with a single one, because some parallel mechanisms used by the database system depend on the number of configured data devspaces.
For performance reasons, the log devspaces must not be created on RAID-5 systems but only on dedicated disks or RAID-1 systems.
If swap or paging areas and log entries are kept on the same disk, performance will be negatively affected.
UNIX: Raw devices should be used for the data devspaces and log devspaces, because accessing to data in raw devices is generally quicker than accessing data in files.