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What is RAID

Redundant

Array ofIndependent

Disks

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Lets Talk about Striping

RAID arrays that usestriping

improve performance by

splitting up files into small

pieces and distributing themto multiple hard disks.

File Red 140KB

File

Blue

600KB File Green 3.2MB

File Purple 21.2MB

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Two Basic Types of Striping

Striping is available in two forms:

Single-user

also called "large block sequential access

Multi-user sometimes called "small block random access"

Single-user striping improves

performance by parallel data transfer Multi-user striping improves

performance by overlapped seeks

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Block Diagram of a

Raid Striping Configuration

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RAID 0 (Nonredundant)

Striped disk array without fault tolerance.

Best I/O performance achieved when data is striped

across multiple controllers with only one drive per

controller.

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RAID 1 (Mirroring)

For highest performance, the controller must be able

to perform two concurrent separate reads per

mirrored pair or duplicate writes per mirrored pair.

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RAID 0+1(Mirrored Striping)

High data transfer performance.

High I/O rates are achieved thanks to multiple stripe

segments.

Uses mirroring and striping.

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RAID 2 (Memory-Style ECC)

Uses Hamming Codes to detect and correct errors.

The ECC code verifies correct data or corrects single

disk (bit) errors.

Extremely high data transfer rates possible.

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RAID 3 (Bit-Interleaved Parity)

Parallel transfer with parity on the data block issubdivided (striped) and written the data disks.

Stripe parity is generated on writes, recorded on the

parity disk and checked on reads

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RAID 4 (Block-Interleaved Parity)

Independent data disks with shared parity disk.

Each entire block is written onto a data disk.

Parity block for the same rank blocks is generated

on writes, recorded on the parity disk and checked

on reads.

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RAID 5

(Block-Interleaved Distributed Parity)

Each entire data block is written on a data disk.

Parity for blocks in the same rank is generated onwrites, recorded in a distributed location andchecked on reads.

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RAID 6 (P+Q Redundancy)

Independent data disks with two Independent parity

schemes to protect against multiple disk

Data is striped on a block level across a set of

drives, just like RAID 5.

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RAID 7 (Proprietary)

Optimized asynchrony for high I/0 Rates as well ashigh data transfer rates.

Overall write performance is 25% to 90% better thana single spindle performance and 1.5 to 6 timesbetter than other array levels.

Based on RAID 3 and 4. Created by Storage Computer Corporation.

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RAID 10 (Striped Mirroring)

Also known as RAID 1+0 and 1/0 Very high reliability combined with high

performance.

High I/O rates are achieved by striping RAID 1

segments.

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RAID 53 (Striped Array of Arrays)

High I/O rates and data transfer performance High data transfer rates are achieved thanks to its

RAID 3 array segments.

High I/O rates for small request are achieved thanks

to its RAID 0 striping.