A note about RAID
Recent developments in disk technology have made RAID (Redundant Arrays of Inexpensive Disks) a popular option on many systems. Often, when the term RAID is used, hardware administrators immediately think of RAID level 5 (or RAID-5), which allows multiple disk devices to be combined to form one large device. By allocating one device for the storage of redundant data, a RAID-5 disk array is protected from the failure of any single disk in the array, and is often hot swappable, which means that a failing disk can be replaced even as the other drives continue to function, with no need to shut down the system.
RAID-5 is, in fact, very powerful and inexpensive. It is also a technology to be avoided in most cases when configuring your Oracle database! This may seem a harsh statement, but the reality is that although RAID-5 provides good levels of data protection at a low monetary cost, this comes at a very high cost for disk I/O. In particular, write operations on RAID-5 arrays can be orders of magnitude slower than the same operations on a single disk.
A good alternative to the RAID-5 array is the use of RAID level 1, commonly known as disk mirroring. Although more expensive than RAID-5 (one-half of the disks are used for storing redundant data), RAID-1 provides complete data protection with no sacrifice in I/O efficiency.
Warning
RAID-1 requires sufficient hardware resources. In particular, since each write operation actually results in two writes to disk, the load on ...
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