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What is RAID

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What is RAID Redundant Array of Independent Disks Let s Talk about Striping RAID arrays that use striping improve performance by splitting up files into small ... – PowerPoint PPT presentation

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Title: What is RAID


1
What is RAID
  • Redundant
  • Array of
  • Independent
  • Disks

2
Lets Talk about Striping
  • RAID arrays that use striping improve performance
    by splitting up files into small pieces and
    distributing them to multiple hard disks.
  • File Red 140KB
  • File Blue 600KB
  • File Green 3.2MB
  • File Purple 21.2MB

3
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

4
Block Diagram of a Raid Striping Configuration
5
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.

6
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.

7
RAID 01(Mirrored Striping)
  • High data transfer performance.
  • High I/O rates are achieved thanks to multiple
    stripe segments.
  • Uses mirroring and striping.

8
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.

9
Parity Bit Quiz
  • 1. What is a parity bit is used for?
  • single-bit error detection and correction.
  • 2. What are the two types of parity bit
    calculations?
  • even and odd
  • 3. What is the goal of even parity?
  • to have an even number of 1 bits
  • 4. What is the goal of odd parity?
  • to have an odd number of one bits
  • 5. If the sending port reads odd parity and the
    receiving port counts seven 1s in the packet,
    the parity bit is set to what?
  • a 0 bit
  • 6. If the sending port reads even parity and
    the receiving port counts seven 1s in the
    packet, the parity bit is set to what?
  • a 1 bit

10
RAID 3 (Bit-Interleaved Parity)
  • Parallel transfer with parity on the data block
    is subdivided (striped) and written the data
    disks.
  • Stripe parity is generated on writes, recorded on
    the parity disk and checked on reads

11
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.

12
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
    on writes, recorded in a distributed location and
    checked on reads.

13
RAID 6 (PQ 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.

14
RAID 7 (Proprietary)
  • Optimized asynchrony for high I/0 Rates as well
    as high data transfer rates.
  • Overall write performance is 25 to 90 better
    than a single spindle performance and 1.5 to 6
    times better than other array levels.
  • Based on RAID 3 and 4.
  • Created by Storage Computer Corporation.

15
RAID 10 (Striped Mirroring)
  • Also known as RAID 10 and 1/0
  • Very high reliability combined with high
    performance.
  • High I/O rates are achieved by striping RAID 1
    segments.

16
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.
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