1. Abstract

This document
will represent hard disk mirroring method and characteristics , advantages and
disadvantages , Points of failure .

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2. Introduction

The term RAID was coined in 1987
by David Patterson, Randy Katz and Garth A. Gibson. In their 1988 technical
report.

Disk mirroring or it’s called
“Redundant Array of Independent Disks”

 (RAID) is a technique used to protect computer systems from losing data or
any potential losses due to disk failures. In this technique, Data will
duplicated by saving data in two or more identical hard drives, All hard drives
are connected on one disk controller card. If one hard drive fails, the data
can be taken from other mirrored hard drives.

The figure
below illustrates RAID meaning:

 

3. Problem definition

Disk mirroring
(RAID) is technique found to protect data because any system can be break .
After this calamity data will be available whenever you reach this point .
Also, It increases the data acceleration access.

 

 

4. Related work

A
RAID is a collection of separates disks that contents high execution by
increasing the number of drives used for save , access data. Also, Disk
improves I/O performance and data availability. The physical disk group appears
as a single storage unit or more logical units. RAID systems also improve data
storage availability and fault . Data loss caused by a physical disk failure
can be recovered .

 

As written in
the problem definition section there are many solutions to solve this problem
such as “Placing Related Blocks on Cylinders ” to increase access
speed this technique read on the same cylinder in the same time . And there is many
other related techniques  …

 

5.Comparisim

            5.1 Evaluation

 At the hard disk drive data retrieval
evaluation process, all media obtained goes through an analysis to recognize
the real shape of the drive. Few steps to follow through the hard disk drive
data retrieval, and these comprise the following: 1. The hard disk drive data recovery experts will determine whether the issues are physical,
logical, or both. Issues refer to those that happen in the hardware, while
plausible problems occur on the applications structures.

 

5.2
Criticism

First ,Needing too much of memory capacity ;
Because all data written twice or more. 
It have a complex technology . Furthermore, Replacing and restoring the
data from a large file to smaller one may take long time (one or more day)
depending on the speed of controller .

 

5.3 Gaps

            Frequently RAID server has single controller.
If the server failure will result in all single point of failure. Also , Loss of RAID configuration settings or
system registry can make a failure .

 

6. Discussion

In
the 1988 authors determines six levels of RAID, 0 through 5. This numbering
system content uses of redundant data across the array. This number classified
into three categories: standard, nested and nonstandard RAID levels.

 

In case a drive
fails, Data just have to be copied to the replacement drive.

Access data
transactions are very fast while write data transactions are somewhat slower .

 

7. Conclusion

Hoping that my report
is beneficial and you well understood RAID characteristics.