The standard solution
is called SAME (which stands for stripe and mirror everything). The I/O throughput limits of the disks
are the key limits to overcome, so distributing the I/O needs over many disks allows you to take
advantage of the combined throughputs of many devices. Striping enhances your throughput, which
may improve your performance; mirroring provides support in the case of disk failure.
In addition to that level of physical storage tuning, several other factors should be considered.
The following sections address factors that are external to the database but may have a profound
impact on its ability to access data quickly.
Using Raw Devices
Raw devices are available with most Unix operating systems. When they are used, Oracle bypasses
the Unix buffer cache and eliminates the file system overhead. For I/O-intensive applications,
they may result in a performance improvement of around 20 percent over traditional file systems
(and a slightly smaller improvement over Automatic Storage Management). Recent file system
enhancements have largely overcome this performance difference.
Raw devices cannot be managed with the same commands as file systems. For example, the
tar command cannot be used to back up individual files; instead, the dd command must be used.
This is a much less flexible command to use and limits your recovery capabilities.
NOTE
Oracle files should not reside on the same physical devices as non-
Oracle files, particularly if you use raw devices.
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