1 Jason Drown Mark Rodden (Redundant Array of Inexpensive Disks) RAID

2 RAID Defined An array of multiple inexpensive hard disks to provide redundancy for fault tolerance and improved access/availability. Concept introduced in 1988 by Patterson, Gibson, and Katz at the University of California, Berkley.

3 Striping Multiple drives are partitioned into stripes, and concatenated together to produce one parallel storage unit Allows multiple drives to work simultaneously, transferring data in parallel

4 RAID Level 0 © 1999 Advanced Computer & Network Corporation Also known as "Disk Striping" Data is written in blocks on multiple striped drives Provides higher transfer rates No fault tolerance Note: RAID 0 is technically not a true RAID level, since it provides no redundancy

5 RAID Level 1 © 1999 Advanced Computer & Network Corporation Also known as "Disk Mirroring Writes data twice for 100% redundancy High read rate High overhead (twice as many drives are needed)

6 RAID Level 3/4 © 1999 Advanced Computer & Network Corporation Stripes data across multiple drives Provides a parity drive for recovery RAID 3 stripes at byte level; RAID 4 stripes at block level

7 RAID Level 5 © 1999 Advanced Computer & Network Corporation Stripes at block level Provides a parity for data recovery Parity is spread across multiple disks Very high data read rate Most complex controller design Complex rebuild in the event of disk failure RAID 5 is the most popular level

8 RAID Level 10 Combines striping and mirroring No parity One RAID 0 controller stripes two RAID 1 controllers Like RAID 1, it requires twice as many disks

9 RAID Level 0+1 Combines striping and mirroring No parity One RAID 1 controller mirrors two RAID 0 controllers Like RAID 1, it requires twice as many disks Worse failure behavior than RAID 10 Can read in parallel, unlike RAID 10

10 RAID Revisited Redundant Array of Inexpensive Disks (RAID) provides failure tolerance and improved availability Spreads data over multiple hard disks that act as one large storage unit RAID can be implemented in many ways, each with its own benefits Suitable for servers and systems where fault tolerance is necessary

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