Oracle Database Administration: The Essential Refe

About RAID

Recently, there has been a high degree of interest in the use of RAID (redundant arrays of inexpensive disks) technology over a wide range of server configurations. A variety of RAID implementations, or levels, is now available, as summarized in Table 11.3.

Table 11-3. RAID Implementations

RAID Level	Description	Advantages	Disadvantages
RAID-0	Block striping, no parity	Faster reads	No recovery from disk failure
RAID-1	One-to-one disk mirroring	Fully protected from single disk failure, no degradation of I/O speed	Twice as many disks are required
RAID-0+1	One-to-one mirroring with striping	Faster reads, fully protected from single disk failure	Twice as many disks are required
RAID-3	Byte-level striping with dedicated parity disk	Faster reads, fully protected from single disk failure, only one extra disk required per array	Slower writes, slower recovery from failure
RAID-4	Block-level striping with dedicated parity disk	Faster reads, only one extra disk required per array	Slower writes, slower recovery from disk failure
RAID-5	Block-level striping with distributed parity	Faster reads, fully protected from single disk failure, only one disk required per array, faster recovery from disk failure	Slower writes
RAID-6	Block-level striping with dual distributed parity	Faster reads, fully protected from failure of any two disks	Slower writes, requires two extra disks for each array, slower recovery from disk failure
RAID-7	Performance-enhanced RAID-5 ...