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Oracle Database Administration: The Essential Refe by Brian Laskey, David C. Kreines

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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 ...

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