Introduction
Computer storage devices are used to store huge amounts of data and information permanently. If you want any of your data kept safe and lastingly, then your choice should be these devices. Usually these kinds of devices are called secondary storage or permanent storage. Sequential and direct are the two kinds of methods used to access data from secondary devices. Storage devices are the building blocks of storage in disk subsystems as well as being used as standalone products in server systems.
Storage and its Needs
With hard drives now storing tons of data and SSDs becoming more and more common, your computer‘s storage can now range from 64GB to 3TB. That is a pretty big range.However, with the ability to extend a computer‘s storage capacity with external hard-drives, opting for a computer with the greatest amount of storage is no longer a necessity, but rather beneficial. Not every person has unlimited amounts of resources to buy a computer with boundless amounts of storage. Although purchasing a device with minimal storage isn't the proper strategy either, identifying the specific needs for the device is essential. People using their computer to simply access documents and the internet may not want to delve into theirwallet to buy a top-of-the-line device, while workers using their computers to store documents, spreadsheets, presentations and any other file may look to more expensive devices with greater storage.
Computers and other Memory Storage Devices
Computers have limited memory capacity, even though we have lots of additional external aids for memory storage like external hard disks, flash memories, memory cards etc. These devices are just electronic devices which store data in a particular format. These data gets distributed around various sectors on a compact disk or the memory slot. These are stored in a language which are only 0 & 1. They can be arranged, edited, formatted, and retrieved when ever required. There is a greater flexibility in using such memories. They take few seconds to retrieve from their memory space.
Application of Storage device
- These memory storages are used at hazardous areas like nuclear reactors to monitor and store records.
- These are also used in Black Boxes of an aircraft to store data‘s which remains undistracted even after plane crash.
- The data‘s stored in storage device are just like cargoes stored onboard a ship.
Let us say for e.g. we have a computer of memory 160 GB. So we can store data s up to say 140 GB easily. After that there is always a limitation that it can no more accept data . The effect of such huge memory storage results in slowing down the processor. So the speeds of retrieval or any operation performed are slow.
Storage Evaluation Units
Primary Storage
Primary storage, also known as main storage or memory, is the main area in a computer in which data is stored for quick access by the computer's processor. On today‘s smaller computers, especially personal computers and workstations, the term random access memory (RAM) -or just memory is used instead of primary or main storage, and the hard disk, diskette, CD, and DVD collectively describe secondary storage or auxiliary storage.
The terms main storage and auxiliary storage originated in the days of the mainframe computer to distinguish the more immediately accessible data storage from storage that required input/output operations. An earlier term for main storage was core in the days when the main data storage contained ferrite cores. Primary storage is sometimes used to mean storage for data that is in active use in contrast to storage that is used for backup purposes.
Secondary Storage
Secondary storage devices, as indicated by the name, save data after it has been saved by the primary storage device, usually referred to as RAM (Random Access Memory). From the moment you start typing a letter in Microsoft Word, for example, and until you click on ―Save,your entire work is stored in RAM.
However, once you power off your machine, that work is completely erased, and the only copy remaining is on the secondary storage device where you saved it, such as internal or external hard disk drive, optical drives for CDs or DVDs, or USB flash drive. As a result, additional memory, called auxiliary memory or secondary storage, is used with most computer system.
- Secondary storage is non-volatile and has lower cost per bit stored but it generally has an operating speed far slower than that of primary storage.
- It is used primarily to store large volume of data on permanent basis that can be partially transferred to primary storage. whenever required for processing.
Hard Disk
Construction
The basic physical construction of a hard disk drive consists of spinning disks with heads that move over the disks and store data in tracks and sectors. The heads read and write data in concentric rings called tracks, which are divided into segments called sectors, which typically store 512 bytes each (see Figure). Hard disk drives usually have multiple disks, called platters, that are stacked on top of each other and spin in unison, each with two sides on which the drive stores data. Most drives have two or three platters, resulting in four or six sides, but some PC hard disks have up to 12 platters and 24 sides with 24 heads to read them.The identically aligned tracks on each side of every platter together make up a cylinder.
The tracks and sectors on a disk.
Operation
A hard disk drive usually has one head per platter side, with all the heads mounted on a common carrier device or rack. The heads move radially across the disk in unison; they can't move independently because they are mounted on the same carrier or rack, called an actuator. Originally, most hard disks spun at 3,600rpm—approximately 10 times faster than a floppy disk drive. however, most drives spin even faster. Although speeds can vary, modern drives typically spin the platters at either 4,200rpm; 5,400rpm; 7,200rpm; 10,000rpm; or 15,000rpm. Most standard-issue drives found in PCs today spin at 5,400rpm, with high performance models spinning at 7,200rpm. Some of the small 2 1/2'' notebook drives run at only 4,200rpm to conserve power, and the 10,000rpm or 15,000rpm drives are usually found only in very high-performance workstations or servers, where their higher prices, heat generation, and noise can be more easily dealt with. High rotational speeds combined with a fast head-positioning mechanism and more sectors per track are what make one hard disk faster overall than another. The heads in most hard disk drives do not (and should not!) touch the platters during normal operation.
Hard disk cylinders.
However, on most drives, the heads do rest on the platters when the drive is powered off. In most drives, when the drive is powered off, the heads move to the innermost cylinder, where they land on the platter surface. This is referred to as contact start stop (CSS) design. When the drive is powered on, the heads slide on the platter surface as they spin up, until a very thin cushion of air builds up between the heads and platter surface, causing the heads to lift off and remain suspended a short distance above or below the platter. If the air cushion is disturbed by a particle of dust or a shock, the head can come into contact with the platter while it is spinning at full speed. When contact with the spinning platters is forceful enough to do damage, the event is called a head crash. The result of a head crash can be anything from a few lost bytes of data to a completely ruined drive.
Floppy Disk Drives
Most modern personal computers do not have floppy drives anymore. The small, 3 1/2" disks they read only hold 1.44 MB of data so they have become somewhat obsolete when compared to the data storing capabilities of USB flash drives (up to 256 GB) and CD drives (700 MB). Floppies are non-volatile storage. The data remains when the computer power is turned off. They can be read or written to over and over again. The standard types of floppy disk drives and disks that have been used in PCs since the beginning. It explores the various types of drives and disks, how they function, and how to properly install and service them. The high-capacity floppy drives such as the SuperDisk (LS-120 and LS-240) and flash memory devices such as USB keychain are covered separately the floppy is still sometimes used as a system installation and configuration device, especially when troubleshooting. In older systems that don't support the El Torito CD-ROM boot specification,.
Floppy Disk Drives.
the floppy drive is the only way to load an operating system from scratch or to run bootable diagnostics. Newer systems that support El Torito (bootable CDs) do not require floppy drives because they can boot operating systems and diagnostics directly from a CD.
Winchester Disk
An early removable disk drive from IBM that put the heads and platters (disks) in a sealed unit for greater speed. Before the Winchester architecture, removable disks were like removable disks today, in which the read/write heads remain in the drive and make contact with the platter after the cartridge is inserted. Introduced in 1973 as the model 3340, the drive had one permanent and one removable spindle, each holding 30MB.
The Winchester Disk.
The -30-30 storage capacities led to the Winchester nickname after the Winchester 30-30 rifle. The term later referred to all fixed hard disks because the heads and platters are always encased in the same, sealed unit. See also Winchester.The BM‘s Winchester disk was a removable cartridge, but the heads and platters were built in a sealed unit and were not separable. A type of disk storage device characterized by no removable or sealed disk packs; extremely narrow tracks; a lubricated surface that allows the head to rest on the surface during start and stop operations; and servomechanisms which utilize a magnetic pattern, recorded on the medium itself, to position the head.
Optical Disk
An optical disk is mounted on an optical disk drive for reading/writing of information on it. An optical disk drive contains all the mechanical, electrical, and electronic components for holding an optical disk and for reading/writing of information on it. That is, it contains the tray on which the disk is kept, read/write laser beams assembly, and motor to rotate the disk Figure Shows an optical disk drive.
optical disk drive
Zip Drive
A Zip drive is a small, portable disk drive used primarily for backing up and archiving personal computer files. The trademarked Zip drive was developed and is sold by Lomega Corporation. Zip drives and disks come in two sizes. The 100 megabyte size actually holds 100,431,872 bytes of data or the equivalent of 70 floppy diskettes. There is also a 250 megabyte drive and disk. The Lomega Zip drive comes with a software utility that lets you copy the entire contents of your hard drive to one or more Zip disks
Flash Drives(Pendrive)
flash drive is a compact device of the size of a pen, comes in various shapes and stylish designs (such as pen shape, wallet shape etc.), and may have different added features (such as with a camera, with a built-in N1P3lWMA/FM Radio play back for music on the go, etc.). It enables easy transport of data from one computer to another. It is a plug-and-play device that simply plugs into a USB (Universal Serial Bus) port of a computer. The computer detects it automatically as removable drive.
flash drive(pendrive)
No one can read, write, copy, delete, and move data from the computer‘s hard disk drive to the flash drive or from the flash drive to the hard disk drive. One can even run applications, view videos, or play MP3 files from it directly. Once done, it can be simply plugged out of the USB port of the computer and kept into the pocket for being carried anywhere. A flash drive does not require any battery cable, or software, and is compatible with most PCs, desktop, and laptop computers with USB 2.0 port. All these features make it ideal external data storage for mobile people to carry or transfer data from one computer to another. As thename implies, it is based on flush memory storage technology Recall that flash is non-volatile, Electrically Erasable Programmable Read Only Memory (EEPROM) chip. It is a highly -Aid-state storage having data retention capability of more than 10 years.
Available storage capacities are 8MB, 16MB, 64MB, 128MB, 256MB, 512MB, 1GB, 2GB, 4GB, and 8GB. A: of 16MB capacity has 5600 times more storage capacity than a IAMB floppy disk. Figure 9.7 shows a flash drive. It has a main body and usually a port connector cover. The cover is removed or port connector is pushed out when the drive is to be plugged into the USB port of' a computer. The main body usually has a write protect tab, a read/write LED (Light Emitting Diode) indicator, and a strap hole. Some manufacturers also provide software to be used with the drive.
Blu Ray Disk
Blu-ray Disc (BD) is a next-generation optical disc format meant for storage of high- definition video and high-density data. The Blu-ray standard was jointly developed by a group of consumer electronics and PC companies called the Blu-ray Disc Association (BDA). As compared to the HD DVD format, its main competitor, Blu-ray has more information capacity per layer, 25 instead of 15 gigabytes, but may initially be more expensive to produce.
Memory Card
These disks operate like the common hard disk. But have less storage space, consumes less power and data can be accessed quickly. Its ease of usage makes acceptable, however it is susceptible to virus attack and failure. You should not hold your data permanently on these types of disks; rather you should use them to hold copy files on which you are going to work now. Do not use these disks as a temporary storage device.
