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Mass Storage Structure in Operating Systems

In this tutorial, we will learn about Mass Storage Structure in Operating Systems. We know that there are different types of Storage Devices which are present in the Operating Systems.

Now, we are going to learn about each and every mass storage device in detail. But before learning about them let us know about what is a primary and secondary memory.

Primary Memory

A processor or computer initially or directly accesses primary memory while using a computer. It enables a processor to access programs and services that are now in use and temporarily stored in a particular area of memory.

Primary storage and main memory are the other terms which can be used as a substitute to the term primary memory.

The volatile storage component of a computer system is primary memory. Although there may be data buses, cache memory, or Random Access Memory (RAM), RAM is the most common example for primary memory.

An operating system (OS), user interface, and any user-installed and running software utilities are all loaded into main memory as soon as a computer turns on. When a program or application is launched from main memory, it communicates with the system processor to carry out all of its unique functions.

Secondary memory is said to be slower than primary memory.

Secondary Memory

Secondary memory is non-volatile, permanent computer memory that is not directly accessible by a computer or processor. Data that can be quickly and easily retrieved, transmitted, and utilized by apps and services can be stored by the user and then used in this manner.

Secondary storage is another name which can be used as a substitute to the word secondary memory.

Read-only memory (ROM), flash drives, hard disk drives (HDD), magnetic tapes, and other forms of internal and external storage media are all considered secondary memory. Only the major or main memory may access secondary memory during computations, and only then is it sent to the processor.

Even if the computer is not powered on, data can be stored and retained in secondary memory, which is slower than primary memory. Additionally, it has large storage capacity, with each memory being capable of holding anywhere from a few megabytes (MB) to many terabytes (TB).

Secondary memory is said to be slower than primary memory.

All the mass storage media belongs to the secondary memory.

Difference between Primary Memory and Secondary Memory

S. No Primary Memory Secondary Memory
1.) Primary Memory is also primarily known as main memory or primary storage memory Secondary Memory is also primarily known as secondary memory storage
2.) They are also known as Internal Memory They are also known as Auxiliary Memory or Backup Memory or Additional Memory.
3.) Primary Memory is more costlier than Secondary Memory Secondary Memory is less costlier than Secondary Memory
4.) Primary memory is said to be faster than Secondary memory. Secondary memory is said to be slower than primary memory.
5.) It stores information or data that the processing unit is currently using. Usually, capacity ranges from sixteen Giga Bytes (16 GB) to Thirty Two Giga Bytes (32 GB). It has a substantial amount of information and data storage. Typically, capacity ranges from 200 GB to terabytes.
6.) The Primary Memory can be divided as Volatile and Non Volatile Memories The Secondary Memory can only be classified as Non Volatile Memory only.
7.) Data cannot be preserved in the event of a power outage since it is a volatile memory. Because it has a non-volatile memory, the information may be kept even in the event of a power outage.

Now, let us learn about the types of the Mass Storage Media which are present in the market.

Mass Storage Structure

Systems designed to store enormous volumes of data are referred to as mass storage devices. Massive storage devices are sometimes used interchangeably with peripheral storage, which is the management of bigger volumes of data that are larger than the native storage capability of a computer or device.

The basic idea of Mass Storage is to create a Data Backup or Data Recovery System.

Along with computer systems, definitions of mass storage technologies and tactics have changed. The earliest and most basic mass storage techniques date back to the era of main frame supercomputers, according to experts. Punch cards, Hollerith cards, and other relatively similar manual storage medium are examples of this Mass Storage Media these days. Today, mass storage may include several kinds of hard disks or solid-state storage devices, as well as tape drives and other physical data storage devices.

The concepts of data backup and data recovery are frequently linked to mass storage media. The biggest Business Companies will make plans for recording, storing, and backing up all accessible data, which calls for a lot more mass storage media than what factory-direct gear can provide. This suggests a method for handling continuous mass storage that uses tape or other media. Other kinds of mass storage could function well as a data storage plan for a big network or a bunch of mobile distant devices. To backup data on a portable tablet that doesn't have a lot of internal capacity, for instance, mass storage for a tablet might require the usage of flash or Universal Serial Bus media (USB Media).

The Mass Storage Structure Devices are:

  1. Magnetic Disks
  2. Solid State Disks
  3. Magnetic Tapes

Magnetic Disks

Now, we are going to know about all whereabouts of the Magnetic Disk Mass Storage Structure Devices.

The process of magnetization is used to write, rewrite, and access data on a magnetic disk, a storage device. This process is known as Magnetic Disk. It is coated magnetically and has tracks, spots, and sectors for storing data.

In 1956, IBM created the first magnetic hard drive, a substantial device with 50 21-inch (53-cm) platters. Despite being large, it could only hold 5 megabytes of information. Since then, magnetic disks' storage capabilities have multiplied dramatically while simultaneously shrinking in size.

Basic Common Examples of Magnetic Disks are:

  1. Floppy Disks
  2. Hard Disks
  3. Zip Disks

The Magnetic Disk basically looks like:

Mass Storage Structure in Operating Systems

Structure and Working of Magnetic Disks:

The basic structure of Magnetic Disks is:

A mechanical arm that travels across a revolving magnetic surface, known as the platter, makes up the majority of a magnetic disk. They come together to make a "comb." Both reading from and writing to the disk are done using the mechanical arm. A magnetization process is used to read and write data on magnetic disks.

One or more disk-shaped platters with magnetic material covering them. Unlike "floppy" disks, which are composed of more flexible plastic, hard disk platters are built of stiff metal.

There are two work areas on each plate. The very top and bottom surfaces of a stack of platters were occasionally avoided by older hard disk drives because they are more prone to damage or even breaking in some cases.

The arm's head slides across the platter's surface while it continues to spin rapidly. The head floats on a small layer of air since the entire apparatus is hermetically sealed. Tiny patches on the disk surface are magnetized and data is saved when a small current is delivered to the head. When the head needs to read the data, a little current could be delivered to such tiny locations on the platter.

On the disk, data is arranged in sectors and tracks, with tracks serving as the disk's spherical divisions. Blocks of data are separated into sectors, which are a subset of tracks. The sectors are where the magnetic disk's read and write operations are carried out. Because the tracks are so close together, the floating heads need to be controlled extremely precisely while reading or writing data.

The tracks are a series of concentric circles that separate each working surface. A cylinder is a group of tracks that are all at the same distance from the platter's edge, or in the accompanying figure, all the tracks that are directly above one another.

A piece track is further split into sectors, generally storing 512 bytes of data each, however some newer drives occasionally employ greater sector sizes.

(Sectors also include a header and a trailer, which among other things contain checksum data. Although internal fragmentation and the quantity of disk that has to be designated bad in the event of mistakes are increased by larger sector sizes, the percentage of the disk used by headers and trailers is reduced.)

Read-write heads are used to read data from hard drives. In the typical setup (shown below), one head is used for each surface, mounted on a separate arm, and moved concurrently from one cylinder to the next by a shared arm assembly. (Other designs, such as separate read-write heads, might accelerate disk access but present significant technical challenges.)

The number of heads (or working surfaces) times the number of tracks per surface times the number of sectors per track times the number of bytes per sector equals the storage capacity of a conventional disk drive. The head-sector-cylinder number of a specific physical block of data can be used to identify it.

The time needed to move the heads from one cylinder to another and for the heads to settle down after the transfer is known as the positioning time, also known as the seek time or random access time. This is usually the stage that moves slowly and is the main obstacle to high transfer rates.

The time it takes for the requested sector to spin and enter the read-write head is known as the rotational latency.

This can be anything from 0 and 1 complete revolutions, with an average of 12 revolutions. This is a physical action that often follows seek time as the second-slowest step. (If a disk rotates at 7200 revolutions per minute, the average rotational delay is 1/2 revolution / 120 revolutions per second, or just over 4 milliseconds, a long time by computer standards.

The amount of time needed to electronically transmit data from a disk to a computer is called the transfer rate. (Some writers could also use the phrase "transfer rate" to refer to the entire transfer rate, which includes search time, rotational delay, and the transfer rate of electronic data.)

Over the surface, disk heads "fly" on a paper-thin air cushion. In the event that they should unintentionally make contact with the disk, a head crash takes place, which may or may not permanently harm or even entirely destroy the disk. Due of this, it is customary to park the disk heads while shutting off a computer, which entails moving the heads off the disk or to an empty space on the disk.

Typically, floppy disks are removeable. Hard drives may also be taken out and replaced with fresh ones, and some of them can even be swapped out while the computer is still functioning.

The I/O Bus, a connection used to connect disk drives to computers, is used for this purpose. Enhanced Integrated Drive Electronics (EIDE), Advanced Technology Attachment (ATA), Serial ATA (SATA), Universal Serial Bus (USB), Fiber Channel (FC), and Small Computer Systems Interface (SCSI) are a few of the popular interface types.

The disk controller is included within the disk itself, whereas the host controller is located at the I/O bus's computer end. Via Input Output ports, the CPU sends orders to the host controller. The disk controller moves information from the onboard cache to the host controller and motherboard memory at electronic speeds after moving information between the magnetic surface and onboard cache.

Solid State Disks

Old technologies are frequently employed in new ways as economic conditions and technology evolve. The growing usage of solid state drives, or SSDs, is one illustration of this.

SSDs function as a tiny, quick hard disk using memory technology. To maintain the information over power cycles, certain implementations may employ either flash memory or DRAM chips protected by a battery.

Due to the lack of moving components, SSDs operate far more quickly than conventional hard drives, and some issues, such the scheduling of disk accesses, simply do not exist.

SSDs do have certain drawbacks, too, including the fact that they cost more than hard drives, are often smaller, and may have shorter life spans.

As a high-speed cache for information on hard disks that has to be retrieved fast, SSDs are particularly helpful. One use is to store frequently requested file system meta-data, such as directory and I node information. A boot drive is another version that has the OS and certain application executables but no essential user data. In order to make laptops thinner, lighter, and quicker, SSDs are also employed in them.

The throughput of the bus may become a limiting problem due to how much quicker SSDs are than conventional hard drives, which leads to certain SSDs being linked directly to the system PCI bus.

Magnetic Tapes

Prior to the advent of hard disk drives, magnetic tapes were frequently utilized for secondary storage; today, they are mostly used for backups.

It might take a while to get to a specific location on a magnetic tape, but once reading or writing starts, access rates are on par with disk drives.

Tape drive capacities may be anywhere from 20 and 200 GB, and compression can increase that capacity by double.

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