So we are going are going to study about R.A.I.D. this is something new that i tried till this is theory based only so there is some or no images only so be bored in just reading just take break and then start again . So the first thing to start this series is R.A.I.D or Redundant Array of Independence Disks.
So here we start ......
R.A.I.D :
R.A.I.D (Redundant Array of Independence Disks)
A disk subsystem that increases performance or provides fault tolerance or both. RAID uses two or more physical disk drives and a RAID controller, which is plugged into motherboards that do not have RAID circuits.
Data is distributed across the drives in one of several ways, referred to as RAID levels, depending on the required level of redundancy and performance. The different schemes, or data distribution layouts, are named by the word "RAID" followed by a number, for example RAID 0 or RAID 1. Each schema, or RAID level, provides a different balance among the key goals: reliability, availability, performance, and capacity. RAID levels greater than RAID 0 provide protection against unrecoverable sector read errors, as well as against failures of whole physical drives.
The term "RAID" was invented by David Patterson, Garth A. Gibson, and Randy Katz at the University of California, Berkeley in 1987. In their June 1988 paper "A Case for Redundant Arrays of Inexpensive Disks (RAID)", presented at the SIGMOD conference, they argued that the top performing mainframe disk drives of the time could be beaten on performance by an array of the inexpensive drives that had been developed for the growing personal computer market. Although failures would rise in proportion to the number of drives, by configuring for redundancy, the reliability of an array could far exceed that of any large single drive.
If you want to use R.A.I.D.then you need two hard disks in your system of same size.
As per the demands of the customer there is many upgraded versions of R.A.I.D. comes in
the market and the corns of the previous versions are improved in the next versions .
So the improvements are listed here from oldest to latest ......
R.A.I.D 0:
In this type there is no mirroring of the data or any copy of data is there in the hard disks.
only the data is distributed into two parts and stored into two parts in two disks .
A broken spanned volume at least preserves the files on the unfailing disks. The benefit of RAID 0 is that the through put of read and write operations to any file is multiplied by the number of disks because, unlike spanned volumes, reads and writes are done , and the cost is complete vulnerability to drive failures.
R.A.I.D 1:
In this type of R.A.I.D. there is some improvements are there from the previous versions of the
R.A.I.D.This consists of data mirroring, without parity or striping. Data is written identically to two drives, thereby producing a "mirrored set" of drives. Thus, any read request can be serviced by any drive in the set.Write throughput is always slower because every drive must be updated, and the slowest drive limits the write performance. The array continues to operate as long as at least one drive is functioning.
R.A.I.D 2:
In this R.A.I.D. there is bit level striping and there is dedicated Hammer code parity. This level is of historical significance only; although it was used on some early machines (for example, the thinking machines CM-2), as of 2014 it is not used by any commercially available system.
R.A.I.D 3:
In this R.A.I.D. there is block level striping and there is dedicated distributed parity.
This is not the R.A.I.D. which is commenlly used in that era.
R.A.I.D 4:
In this R.A.I.D. there is block level striping and there is dedicated distributed parity.
In August 2012, Dell posted an advisory against the use of RAID 5 in any configuration on Dell Equal Logic arrays and RAID 50 with "Class 2 7200 RPM drives of 1 TB and higher capacity" for business-critical data.
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