Databases are saved in file formats, which contain records. At physical level, on some device, there are some actual data which is stored in the electromagnetic format. These storage space gadgets can be broadly categorized into three types −
Primary Storage − The storage space that is directly accessible to the CPU comes under this category.
CPU’s internal storage space (registers), fast memory (cache), and main memory (RAM) are directly accessible to the CPU, as they are all placed on the motherboard or CPU chipset.
This storage space is typically very small, very fast, and unstable.
For maintaining the data, this storage requires continous supply of power.
In case of a power failure, all its information is lost.
Join the dba certification course to know about storage space.
Secondary Storage − Secondary storage space used to storedatathrough backup.
This storage includes storage gadgets that are not a part of the CPU or motherboard, for example, magnetic disks, optical disks (DVD, CD, etc.), hard disks, flash drives, and magnetic tapes.
Tertiary Storage − Tertiary storage space is used for storing large number of data.
Since such storage space gadgets are external to the pc, they are the slowest in rate. These storage space mostly used to take the back up of an entire system. Optical disks and magnetic tapes are widely used as tertiary storage space.
A pc has a well-defined hierarchy of storage. A CPU can access main storage as well as its inbuilt signs up.
The access time of the main storage is obviously less than the CPU rate.
To minimize this rate mismatch, cache memory is introduced. Cache storage provides the fastest accessibility time and it contains information that is most frequently accessed by the CPU.
The storage with the fastest accessibility is the costliest one. Larger storage space gadgets offer slow rate and they are less expensive, however they can store large numbers of information as compared to CPU signs up or storage cache storage.
Hard disk drives are the most common secondary storage space gadgets in the current generation of computers.
Magnetic disk is the name given to it, because they use the concept of magnetization to store information.
Hard disk consist of metal disks coated with magnetizable material. These disks are placed vertically on a spindle.
A read/write head moves in between the disks and is used to magnetize or de-magnetize the spot under it. A magnetized spot can be recognized as 0 (zero) or 1 (one).
Hard disks are formatted in a well-defined order to store information efficiently. A hard disk plate has many concentric circles on it, called tracks. Every track is further divided into sectors. A sector on a difficult drive typically stores 512 bytes of information.
Redundant Range of Independent Disks
RAID or Redundant Array of Independent Disks, is a technology to connect several secondary storage space gadgets and use them as a single storage space media.
RAID consists of an array of disks in which several disks are connected together to achieve different goals.
RAID levels define the use of hard disk arrays.
In this stage, a striped range of disk is implemented. The information is broken down into prevents and the prevents are distributed among pushes. Each difficult drive receives a prevent of information to write/read in parallel. It enhances the pace and performance of the difficult drive. There is no equality and backup in Level 0.
RAID 1 uses mirroring techniques. When information is sent to a RAID controller, it makes a copy of the data and then forward it to the array of disks. RAID stage 1 is also called mirroring and provides 100% redundancy in case of a failure.
RAID 2 stores Error Correction Code using Hamming distance for its information,shared on different disks. Like stage 0, each information bit in a word is recorded on a separate disk drive and ECC codes of the information words are saved on a different set pushes. Due to its complex structure and high cost, RAID 2 is not commercially available.
RAID 3 shares the information onto several disks. The equality bit produced for information word is saved on a different difficult drive. This technique makes it to overcome single disk drive failures.
In this stage, an entire combination of data is written onto information pushes and then the equality is produced and saved on a different disk drive.
Note that stage 3 uses byte-level striping, whereas stage 4 uses block-level striping. Both stage 3 and stage 4 require at least three disk for implementation of RAID.
RAID 5 writes whole information combined onto different disks, but the equality bits produced for information combined stripes are distributed among all the information disks rather than storing them on a different dedicated difficult drive.
RAID 6 is an extension of stage 5. In this stage, two independent parities are produced and saved in shared fashion among several pushes. Two parities provide additional fault tolerance. This stage requires at least four hard disk drives for application of RAID.
Thus our dba institute in Pune is more than enough for you to make your career in this field.