What
is RAID
RAID stands for Redundant
Array of Independent Disks . RAID is a method of combining several
hard disks into one unit or group.It is a data storage Virtualization
technology that combines multiple disk components into a logical unit for the
purposes of data redundancy or performance improvement. It also offers
fault tolerance role and higher throughput levels than a single hard disk or
group of independent hard disks. RAID levels 0, 1, 5, 6 and 10 are
the most popular configurations.
RAID Step and Configurations
performance
performance
RAID
0 splits data across disks,
resulting in higher data throughput. The performance of this configuration is
extremely high, but a loss of any disk in the array will result data loss.
This level is commonly known to as striping.
Minimum
number of disks required are: 2
Performance: High
Redundancy: Low
Efficiency: High
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Disadvantages:
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RAID
1 writes all data to two or
more disks for 100% redundancy: if either disk fails, no data is lost.
Compared to a single disk, RAID 1 tends to be fast on reads, slow on writes.
This is a good entry-level redundant configuration. However, since an entire
disk is a duplicate, the cost per MB is high. This is commonly known to
as mirroring.
Minimum
number of disks required are: 2
Performance: Average
Redundancy: High
Efficiency: Low
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Disadvantages:
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RAID
5 stripes data in a block level across
several disks, with parity equality distributed among the
disks. The parity information allows recovery from the failure of any single
disk. Write performance is rather quick, but due to parity data must be
skipped on each disk during reads, reads are slower. The low ratio of parity
to data means low redundancy overhead.
Minimum
number of disks required are: 3
Performance: Average
Redundancy: High
Efficiency: High
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Disadvantages:
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RAID
6 is an upgrade version from
RAID 5: data is striped in a block level across several
disks with double parity distributed
among the disks. As in RAID 5, parity information allows recovery from the
failure of any single disk. The double parity gives RAID 6 additional
redundancy at the cost of lower write performance (read performance is the
same), and redundancy overhead remains low.
Minimum
number of disks required are: 4
Performance: Average
Redundancy: High
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Disadvantages:
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RAID
0+1 is a mirror (RAID 1) array
whose segments are striped (RAID 0) arrays. This configuration
combines security of RAID 1 with an extra performance boost from the RAID 0
striping.
Minimum
number of disks required are: 4
Performance: Very High
Redundancy: High
Efficiency: Low
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Disadvantages:
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RAID
10 is a striped (RAID
0) array whose segments are mirrored (RAID 1). RAID 10 is a popular configuration for
today environments where high performance and security are required. In terms
of performance it is similar to RAID 0+1. However, it has superior fault
tolerance and rebuilds performance.
Minimum
number of disks required are: 4
Performance: Very High
Redundancy: Very High
Efficiency: Low
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Disadvantages:
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RAID
50 combines RAID 5
parity and stripes it as in a RAID 0 configuration.
But high in cost and complexity, performance and fault tolerance are superior
to RAID 5.
Minimum
number of disks required are: 6
Performance: High
Redundancy: High
Efficiency: Average
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Disadvantages:
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RAID
60 combines RAID 6
double parity and stripes it as in a RAID 0 configuration.
Although high in cost and complexity, performance and fault tolerance are
superior to RAID 6.
Minimum
number of disks required are: 8
Performance: High
Redundancy: High
Efficiency: Average
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Disadvantages:
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