1. RAID Technology By: Adarsha A,S 1BY08A03

2. Overview What is RAID Technology? What is RAID Technology? History of RAID History of RAID Techniques/Methods Techniques/Methods RAID Levels (RAID0, RAID1RAD2,RAID3, RAID4, RAID5,RAD6,RAID7, RAID10, RAID53,RAD0+1) RAID Levels (RAID0, RAID1RAD2,RAID3, RAID4, RAID5,RAD6,RAID7, RAID10, RAID53,RAD0+1) Conclusion Conclusion

3. What is RAID Technology? RAID is a method of combining several hard disk drives into one logical unit. RAID is a method of combining several hard disk drives into one logical unit. RAID technology was developed to address the fault-tolerance and performance limitations of conventional disk storage. It can offer fault tolerance and higher throughput levels than a single hard drive or group of independent hard drives.

4. History RAID technology was first defined by a group of computer scientists at the University of California in 1987. RAID technology was first defined by a group of computer scientists at the University of California in 1987. The scientists studied the possibility of using two or more disks to appear as a single device to the host system. The scientists studied the possibility of using two or more disks to appear as a single device to the host system. Although the array's performance was better than that of large, single-disk storage systems, reliability was unacceptably low. Although the array's performance was better than that of large, single-disk storage systems, reliability was unacceptably low. To address this, the scientists proposed redundant architectures to provide ways of achieving storage fault tolerance. To address this, the scientists proposed redundant architectures to provide ways of achieving storage fault tolerance. However, it does offer maximum throughput for some data-intensive applications such as desktop digital video production. However, it does offer maximum throughput for some data-intensive applications such as desktop digital video production.

5. Techniques/Methods Mirroring Mirroring Parity Parity 10101010 XOR 11111111 = 01010101 11111111 XOR 01010101 = 10101010 10101010 XOR 01010101 = 11111111

6. Techniques/Methods Striping Striping Data striping, distributes data transparently over multiple disk to make them appear as a single large, fast disk. Data striping, distributes data transparently over multiple disk to make them appear as a single large, fast disk.

7. RAID Levels There are several different RAID "levels", each with inherent, and availability (fault- tolerance) characteristics designed to meet different storage needs. There are several different RAID "levels", each with inherent, and availability (fault- tolerance) characteristics designed to meet different storage needs. No individual RAID level is inherently superior to any other. No individual RAID level is inherently superior to any other. Each of the five array architectures is well- suited for certain types of applications and computing environments. Each of the five array architectures is well- suited for certain types of applications and computing environments. For client/server applications, storage systems based on RAID levels 1 and 5 have been the most widely used. For client/server applications, storage systems based on RAID levels 1 and 5 have been the most widely used.

8. RAID 0 Uses striping Uses striping –I/O performance gain –No Data redundancy Strengths: Highest performance. Strengths: Highest performance. Weaknesses: No data protection; One drive fails, all data is lost. Weaknesses: No data protection; One drive fails, all data is lost.

9. RAID 1 Uses mirroring -Also known as duplexing Uses mirroring -Also known as duplexing Fault tolerant and High Disk overhead Fault tolerant and High Disk overhead – Minimum number of drives: 2 – Strengths: Very high performance; Very high data protection. – Weaknesses: High redundancy cost overhead; Because all data is duplicated twice, so more storage capacity is required.

10. RAID 2 Error Detection and Correction Error Detection and Correction Parity bits are added -Used to identify and correct errors Parity bits are added -Used to identify and correct errors Hamming Code Hamming Code –Uses parity bits to verify data integrity –Strengths: Previously used for RAM error environments correction (known as Hamming Code ) – Weaknesses: No practical use; –Same performance can be achieved by RAID 3 at lower cost.

11. RAID 3: XOR Byte-level data striping. Byte-level data striping. Minimum number of drives: 3 Minimum number of drives: 3 Strengths: Excellent performance for large sequential data requests. Strengths: Excellent performance for large sequential data requests. Weaknesses: Not well-suited for transaction- oriented network applications; Weaknesses: Not well-suited for transaction- oriented network applications; Single parity drive does not support multiple. Single parity drive does not support multiple.

12. RAID 3: Adv and Dis Advantages: High Read/Write Transfer Rates High Read/Write Transfer Rates Disk failures don’t slow the system Disk failures don’t slow the system Low Ratio of Data Disks to Parity Disks Low Ratio of Data Disks to Parity DisksDisadvantages: Transaction rate slowed by Parity Disk Transaction rate slowed by Parity Disk Complex Controller Design. Complex Controller Design.

13. RAID 3: Uses Video Production Video Production High-end Video and Image Editing High-end Video and Image Editing Other uses that require high throughput of data Other uses that require high throughput of data

14. RAID 4 No Striping, Entire files written to individual disks No Striping, Entire files written to individual disks Parity Data created on a sector-by-sector basis. Parity Data created on a sector-by-sector basis.

15. RAID 4: Adv, Dis, and Uses Advantages: Very high read rates Very high read rates –Multiple files read at once Uses: Web Servers, and other high read, low write situations Web Servers, and other high read, low write situationsDisadvantages: Very slow write rates Very slow write rates Inefficient data recovery Inefficient data recovery Even more Complex Controller Design than RAID 3 Even more Complex Controller Design than RAID 3 *Has most of the other Advantages and Disadvantages of RAID 3

16. RAID 5 Highest Read data transaction rate Highest Read data transaction rate Medium Write data transaction rate Medium Write data transaction rate Most complex controller design Most complex controller design Used For Server Applications. Used For Server Applications.

17. RAID 6 Fault tolerance Fault tolerance Very complex controller design Very complex controller design Very poor write performance Very poor write performance

18. RAID 7 Extremely high cost Extremely high cost Fast access times Fast access times Improved write performance with increasing number of drives Improved write performance with increasing number of drives

19. RAID 10 Uses multiple (mirrored) RAID 1 in a single array Uses multiple (mirrored) RAID 1 in a single array Data striped across all mirrored sets Data striped across all mirrored sets Very high fault tolerance Very high fault tolerance High performance rate High performance rate each drive duplicated high implementation cost

20. RAID 53 Consists of a striped array made up of RAID 3 segments Consists of a striped array made up of RAID 3 segments Very expensive Very expensive Achieves high rate of I/O Achieves high rate of I/O

21. RAID 0+1 Acts as a mirrored array whose parts consist of RAID 0 arrays Acts as a mirrored array whose parts consist of RAID 0 arrays Very expensive Very expensive Works well in handling images Works well in handling images –very high data transfer rate – –Not great reliability one disk failure leaves you left with only the characteristics of a striped array (no fault tolerance)

22. Conclusion Grown more complex Grown more complex Large price range Large price range Huge step forward for industry Huge step forward for industry

23. END END