What is RAID Redundant Array of Independent Disks

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.striping File Red 140KB File Blue 600KB File Green 3.2MB File Purple 21.2MB

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

Block Diagram of a Raid Striping Configuration

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.

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.

RAID 0+1(Mirrored Striping) High data transfer performance. High I/O rates are achieved thanks to multiple stripe segments. Uses mirroring and striping.

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.

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

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

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.

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.

RAID 6 (P+Q 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.

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.

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

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.