Question

Describe the concept of RAID and compare its various levels in about 300 words on the following parameters:

1. Cost

2. Availability

3. Response time

4. Reliability

Answer 1

Raid known as "Redundant Array of Independent Disks" or "Redundant Array of Inexpensive Disks"

Raid is used for creating large reliable data stores from multiple hard disk drives and used for increasing the performance and reliability of data storage .

levels of Raid:

There are 6 levels of Raid:

Raid 0:This level splits data evenly across two or more disks without parity information.It contains redundancy and provides fault tolerance .The failure of one drive will cause entire array to fail.It is mostly used to increase performance.This response time is better than a single drive..Poor performance.

Raid 1: This level consists of an exact copy of a set of data on two or more disks.This level offers no parity across multiple disks.This is useful when read performance is more important than write performance.overall response time is equal to the speed of the slowest disk. less compare to Raid 2.

Raid 2::This level is rarely used in practice,strips data at the bit level and uses a hamming code for error correction .Where as this is not currently used level.

Raid 3:This level consists of byte level striping with a dedicated parity disk.It cannot serve multiple requests simultaneously..This level is also rarely used in practice.Price is more .

Raid 4:This level consists of block level striping with a dedicated parity disk.It provides good performance of random reads.while the performance of random writes is low due to the need to write all parity data to a single disk.

Raid 5:This level consists of block level striping with distributed parity .It requires at least  3 disks.Upon failure of one disk served by another disk such that no data lose will happen .by removing raid 3 and raid 4 we are using raid 5 consists of features of both .Response time is better than Raid 4 and Raid 3..Price is more compare to other raids.Response is fast when compare to other levels.

Raid 6: This level extends Raid 5 by adding another parity block .It uses block level striping with two parity blocks distributed across all member disks ..

Raid 10: This level is combining Raid 1 and Raid 0 .which offers higher performance than Raid 1 but at a higher cost.The data is mirrored and the mirrors are striped.

Availability of Raid 5 is more compare to other levels.