29-11-2012, 12:18 PM
REDUNDANT ARRAY OF INEXPENSIVE DISKS
raid..pptx (Size: 1.15 MB / Downloads: 33)
In 1987,Patterson,Gibson and Katz at the University of California Berkeley, published a paper entitled “A Case for Redundant Array of Inexpensive Disks (RAID)”
The basic idea of RAID was to combine multiple, small inexpensive disks drive into an array of disks which yeilds performance exceeding that of a Single,Large Expensive Drive(SLED).
Additionally this array of drives appers to the computer as a single logical storage unit or drive.
SOFTWARE AND HARDWARE
RAID can be Software, Hardware or a combination of both. Generally speaking, Software RAID tends to offer duplication or mirroring, whilst Hardware RAID offers Parity-based protection.
Software RAID uses more system resources as more disk ports and channels are required and it is subject to additional load during write and copy operations. Software RAID may have a lower cost than hardware RAID because it has no dedicated RAID controller, but may not have the same hotfix or performance capabilities. Software RAID is needed for mirroring to remote locations.
RAID 0
Striping at the level of blocks.
Data split across in drives resulting in higher data throughout.
Performance is very good but the failure of any disc in the array result in data loss.
RAID 0 commonly referred to as striping.
Reliability Problems : No mirroring or parity bits.
CONCLUSION
RAIDs offers a cost effective option to meet the challenge of exponential growth in the processor and memory speed. We believe the size reduction of personal computer is a key to success of disks arrays, just as Gordon Bell argues that the size reduction of microprocessors is a key to success in multiprocessors.
With advantages in cost-performance , reliability ,power consumption, and modular growth , we except RAIDs to replace SLEDs in future I/O
Systems..