1.2 raid


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1.2 raid

  1. 1. A+ Hardware<br />Section 1.2 RAID<br />Made By : Gagandeep Singh<br />
  2. 2. What you learn today<br />CompTIA A+ 220-701 , Section 1.2,<br />Explain motherboard components, types and features.<br />Contrast RAID<br /> - Level 0<br /> - Level 1 <br /> - Level 5<br />
  3. 3. What you’ll learn today<br />Overview of RAID<br />RAID levels<br />Software RAID vs. Hardware RAID.<br />
  4. 4. RAID<br />
  5. 5. RAID<br />Redundant Array Inexpensive Disks<br /> - They’re also independent disk.<br />Different RAID levels <br /> - Some redundant, some not.<br />RAID 0 – Striping<br />RAID 1 – Mirroring<br />RAID 2 – Striping with parity.<br />
  6. 6. RAID 0 <br /><ul><li> Files are split between physical drives .
  7. 7. High performance ( Data written quickly).
  8. 8. Poor redundancy (Drive Failure breaks the array).</li></li></ul><li>RAID 0 - Striping<br />The simplest RAID level, RAID 0 should really be called “RAID”, since it involves no redundancy. <br />Files are broken into stripes of a size dictated by the user-defined stripe size of the array, and stripes are sent to each disk in the array. <br />Giving up redundancy allows this RAID level the best overall performance characteristics of the single RAID levels, especially for its cost. <br />For this reason, it is becoming increasingly popular by performance-seekers, especially in the lower end of the marketplace.<br />
  9. 9. RAID 1<br /><ul><li> Files are duplicated between physical disk.
  10. 10. High Disk Utilization</li></ul> - Every File is duplicated.<br /> - Required disk space is doubled.<br /><ul><li>High Redundancy</li></ul> - Drive failure does not affect data availability.<br />
  11. 11. Advantages <br />One Write or two Reads possible per mirrored pair<br />100% redundancy of data means no rebuild is necessary in case of a disk failure, just a copy to the replacement disk<br />Simplest RAID storage subsystem design<br />
  12. 12. Disadvantage<br />Highest disk overhead of all RAID types (100%) - inefficient<br />Typically the RAID function is done by system software, loading the CPU/Server and possibly degrading throughput at high activity levels. Hardware implementation is strongly recommended<br />
  13. 13. RAID 5 – Striping with parity. <br /><ul><li> Files are striped.</li></ul> - Along with the parity block.<br /><ul><li>Efficient use of disk space.</li></ul> - Files aren’t duplicated, but space is still used for parity.<br /><ul><li> High redundancy</li></ul> - Data is available after disk failure.<br /> - Parity calculation may effect performance. <br />
  14. 14. RAID 5<br />Independent Data Disks with Distributed Parity Blocks<br />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. RAID Level 5 requires a minimum of 3 drives to implement.<br />
  15. 15. Advantage<br />Highest Read data transaction rate<br />Medium Write data transaction rate<br />Low ratio of ECC (Parity) disks to data disks means high efficiency<br />Good aggregate transfer rate<br />
  16. 16. Disadvantages<br />Disk failure has a medium impact on throughput<br />Most complex controller design<br />Difficult to rebuild in the event of a disk failure (as compared to RAID level 1)<br />Individual block data transfer rate same as single disk<br />
  17. 17. Software RAID vs. Hardware RAID<br />Software Based RAID<br /> - A features of the Operating System.<br /> - Doesn’t require any special hardware.<br /> - Usually lower-performance than the hardware performance.<br />Hardware Based RAID<br /> - A feature of hard drive controller.<br /> - Configured outside the OS.<br />Usually invisible to Operating System.<br />High performance, designed for speed.<br />