RAID (Redundant Array of Independent Disks) is a storage technology that combines multiple disk drives into a logical unit. It distributes data across several RAID levels for fault tolerance and improved performance. In 1987, researchers first defined RAID levels 1-5, which standardized how data is striped and mirrored across disks. Today there are several standard RAID levels that provide different balances of performance, capacity, and fault tolerance through techniques like data striping, mirroring, and parity.

1. RAID means redundant array of independent
disk. It is a type of storage technology. It
combines multiple disk component into a logical
unit. Data is distributed across several RAID
levels.

2. Redundant array of independent disk is a
category of disk drives that has two or more
drives in combination for fault tolerance. These
are frequently used in the server. It allows you
to store data in the multiple places (redundantly)
to improve the storage performance.

3. In the 1987 David Patterson, Garth Gibson and
Randy Katz first published their research paper.
Their paper name was “ A case of Redundant
Arrays of Inexpensive Disks”. Which helps to
form the modern RAID industry. Their paper
defined 1 to 5 RAID levels. Today more levels
are defined. This technology remains vibrant as
ever.

4. Number of standard schemes are evolved those
are refer as levels. Originally there ware five
levels but today it vibrantly evolved more levels.
It’s level and original data format is standardize
storage networking industry association (SNIA).

5. RAID means redundant array of independent
disk. It is a type of storage technology. It
combines multiple disk component into a logical
unit. Data is distributed across several RAID
levels.

6. Different architecture are provided by RAID
followed by each architecture provides
performance, capacity and tolerance. These
levels are 0, 1, 2, 3, 4, 5 and 6.

7. Provides data striping (spreading out files across
multiple disk drives) but without redundancy. It
highly improves the performance. In certain case
if one drive is fail then all data is lost. Data is
fragmented is called blocks. Number of block is
dedicated to the stripe size. It is configuration
parameter of array. Block is written in the same
sector simultaneously in the different drives.

8. Level 1 provides the twice the read transaction
rate in the same disk. Write transaction rate is
also same. Write request update the stripe of
both drives. The array is continue to operate as
long as at one drive is operating. It has separate
controller in each drive for simultaneously reads
called multiplexing.

9. Strip data at the bit level rather than the block
level. In this level all disk spindle rotating in a
synchronized way that each sequential bit on a
different drive. Across these bits hamming code
is calculated.

10. It provides byte level striping with a dedicated
parity disk. It can’t service simultaneously it is
used rarely. Parity is calculated and stored in the
dedicated parity drive.

11. Commonly used implementation of RAID is
block level striping with a dedicated parity disk.
If disk fails then parity create a replacement.
Disadvantage of it creates bottleneck.

12. It provides data striping at the block level. It
performs excellently in the good fault tolerance.
It requires data and all drives but one to be
operate. Array is not destroyed in a single disk
failure. In a single disk failure it reduce the
entire performance. RAID 5 requires at least
three disk.

13. It is similar to RAID 5 except instead of one
parity block per stripe. With two independent
parity block RAID 6 can survive loss of two in
among the group of disk.

14. RAID concept is present from in 1986 and it is
installed in the million of configuration. It lacks
of the standard. RAID implementation is
proprietary and unique to every vendor.

15. RAID is implemented in the server by a software
called JBOD (just a bunch of disks). It acts as a
logical volume manager it manage the parity
calculation.

16. These are the cards that can be added to a
server and performs the offload of overloaded
RAID CPU. It is a better solution for a single
server. For managing the mirror data it CPU
spend no processing power. It uses either
internal drives or JBOD.

17. It consist of two high performance and
redundant RAID controller. They support
multiple RAID levels and different drive types
and speeds. Storage array also have snap shot,
volume copy etc. There are different types of
RAID controller like IBM RAID controller.

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