Magnetic Disk

a magnetic disk is a type of data storage that uses magnetic patterns on a circular surface.Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using one or more read/write heads.

A memory device, such as a floppy disk, a hard disk, or a removable cartridge, that is covered with a magnetic coating on which digital information is stored in the form of microscopically small, magnetized needles.



The primary computer storage device. Like tape, it is magnetically recorded and can be re-recorded over and over. Disks are rotating platters with a mechanical arm that moves a read/write head between the outer and inner edges of the platter's surface. It can take as long as one second to find a location on a floppy disk to as little as a couple of milliseconds on a fast hard disk. See hard disk for more details.

Tracks and Spots
The disk surface is divided into concentric tracks (circles within circles). The thinner the tracks, the more storage. The data bits are recorded as tiny magnetic spots on the tracks. The smaller the spot, the more bits per inch and the greater the storage.

Sectors
Tracks are further divided into sectors, which hold a block of data that is read or written at one time; for example, READ SECTOR 782, WRITE SECTOR 5448. In order to update the disk, one or more sectors are read into the computer, changed and written back to disk. The operating system figures out how to fit data into these fixed spaces.

TYPES OF MAGNETIC DISKS

All magnetic disks come in the form of round platters. These disks are available in different sizes, shapes and designs. Some are attached to the read/write head assembly whereas some are available in the form of removable disks. Broadly, magnetic disks can be classified into three types: floppy disk, hard disk and zip disk.

Floppy Disk

A floppy disk is a round, flat piece of Mylar plastic coated with ferric oxide (a rust-like substance containing tiny particles capable of holding a magnetic field) and encased in a protective plastic cover (disk jacket). It is a removable disk and is read and written by a floppy disk drive (FDD), which is a device that performs the basic operation on a disk, including rotating the disk and reading and writing data onto it. The disk drive's read/write head alters the magnetic orientation of the particles, where orientation in one direction represents “1” and orientation in the other represents “0”.

Basically, a floppy disk drive reads and writes data to a small, circular piece of metal-coated plastic similar to audio cassette tape.

• Both use a thin plastic base material coated with iron oxide. This oxide is a ferromagnetic material, meaning that if you expose it to a magnetic field it is permanently magnetized by the field.
• Both can record information instantly.
• Both can be erased and reused many times.
• Both are very inexpensive and easy to use.

A floppy disk, like a cassette tape, is made from a thin piece of plastic coated with a magnetic material on both sides. However, it is shaped like a disk rather than a long thin ribbon. The tracks are arranged in concentric rings so that the software can jump from each file easily. The diskette spins like a record and the heads move to the correct track. The write head puts data on the diskette by magnetizing small, iron, bar-magnet particles embedded in the plastic surface. The magnetized particles have their north and south poles oriented in such a way that their pattern may be detected and read on a subsequent read operation. This type of storage is a common type in all computers.  However due to the small amounts of information able to be held on a magnetic disk, technology has advanced and brought us optical disk drives.  Plastics are used because they are inexpensive to make and you can get similar conductive properties by adding the oxide layer.

Fixed Disk: 
Hard Disk otherwise referred to as HDD. It can have one or more disc platters made of aluminum alloy or glass with a thin magnetic layer bond. These magnetic disks or platters are sealed within the enclosure. Size 1.8", 2.5", 3.5", 5.25", 8", 12"

Zip Disk

Working Of Magnetic Tape

What are Storage devices?

Storage Devices are the data storage devices that are used in the computers to store the data. The computer has many types of data storage devices. Some of them can be classified as the removable data Storage Devices and the others as the non removable data Storage Devices.

Note:
Auxiliary memory, also known as auxiliary storage, secondary storage, secondary memory or external memory, is used to store a large amount of data at lesser cost per byte than primary memory. 

The memory is of two types; one is the primary memory and the other one is the secondary memory.

The primary memory is the volatile memory and the secondary memory is the non volatile memory. The volatile memory is the kind of the memory that is erasable and the non volatile memory is the one where in the contents cannot be erased. Basically when we talk about the data storage devices it is generally assumed to be the secondary memory.

The secondary memory is used to store the data permanently in the computer. The secondary storage devices are usually as follows: hard disk drives – this is the most common type of storage device that is used in almost all the computer systems. The other ones include the floppy disk drives, the CD ROM, and the DVD ROM. The flash memory, the USB data card etc.

Hierarchy of Memory:

Floppy discs

A floppy disk is a data storage medium that is composed of a disk of thin, flexible floppy)magnetic storagemedium encased in asquareor rectangularplasticshell. Floppy disks are read and written by afloppy disk drive.The smallest and most portable of all the storage devices usually holds about 1.44 MB of storage. Use a floppy disk media.

Application

Any use where small files such as word processing, small spreadsheets and databases need to be moved from one computer to another.
Useful to backup small data files.

Fixed hard discs

A hard disk drive is the device used to store large amounts of digital information in computers and related equipment like iPods and games consoles such as the Xbox 360 and PS3.
Hard disk drives are used to store operating systems, software and working data.
These are suitable for any application which requires very fast access to data for both reading and writing to. However, Hard disk drives may not be suitable for applications which need portability.
Almost all computers used a fixed hard disc. Used for on-line and real time processes requiring direct access. Used in file servers for computer networks to store large amount of data.

Portable hard discs

Portable hard discs are good fun because you can carry data about all over the place and transfer information, programs, pictures, etc between computers.A hard drive is usually built inside your computer and holds anywhere from 1GB to 4TB of capacity. There are three types of internal hard drives are PATA, SATA and SCSI. External hard drives comes in USB, Firewire, SATA and SCSI.

Advantages:

• Greatly improved data cargo carrying capacity (relative to the 1.44 Mb floppy disc).
• You don't need to worry about the other person having the same type of special cartridge drive as yourself.

Disadvantages:

• Hard drives have to be handled quite carefully, and when being transported should be wrapped in something soft and put in a padded bag.
• More expensive than other forms of removable media.

Application

Portable disc discs are used to store very large files which need transporting from one computer to another and price is not an issue.

Magnetic tapes

Magnetic tape has been used for data storage for over 50 years. When storing large amounts of data, tape can be substantially less expensive than disk or other data storage options. Tape storage has always been used with large computer systems. Modern usage is primarily as a high capacity medium for backups and archives.  

Drawbacks

Writing and retrieving data is slow.
It uses serial access for reading and writing.

Application

Magnetic tapes are used for application which requires extremely large storage capacity where speed of access is not an issue.
It is commonly used for backups of file servers for computer networks, in a variety of batch processing applications such as reading of bank cheques, payroll processing and general stock control.

Optical backing storage media such as CDs andDVDs

• CDs tend to be used for large files (but smaller than 1Gb) which are too big for a floppy disc to hold such as music and general animation.
• DVDs are used to hold very large files (several Gb) such as movie films. Both CDs and DVDs are portable i.e. they can be transported from one computer to another. Both can be used to store computer data.
• CD ROM/DVD ROM Applications which require the prevention of deletion of data, accidental or otherwise. CDs used by software companies for distributing software programs and data; by Music companies for distributing music albums and by book publishers for distributing encyclopaedias, reference books etc. DVDs used by film distributors.
• CD R/DVD R Applications which require a single ‘burning’ of data, e.g. CDs - recording of music downloads from the Internet, recording of music from MP3 format, recording of data for archiving or backup purposes. DVDs – recording of film movies and television programs.
• CD RW/DVD RW Applications which require the updating of information and ability to record over old data. Not suitable for music recording but is very useful for keeping generations of files. DVDs have between five and ten times the capacity of CDs.

Solid state backing storage

• These are the smallest form of memory available in the market today.
• Widely used as removable storage.
• They are more robust than other forms of storage.
• Though expensive than other forms they can be easily written to and updated.

Memory sticks/Pen drives

USB flash drives are typically removable and rewritable, much smaller than a floppy disk. Storage capacities typically range from 64 MB to 64 GB. USB flash drives offer potential advantages over other portable storage devices, particularly the floppy disk.
They have a more compact shape, operate faster, hold much more data, have a more durable design, and operate more reliably due to their lack of moving parts. Flash drives are widely used to transport files and backup data from computer to computer.

Flash memory cards

A memory card or flash memory card is a solid-state electronic flash memory data storage device used with digital cameras, handheld and Mobile computers, telephones, music players, video game consoles, and other electronics.
Nowadays, most new PCs have built-in slots for a variety of memory cards; Memory Stick, CompactFlash, SD, etc. Some digital gadgets support more than one memory card to ensure compatibility.

Tape Drives

Tape drives allow large companies as well as end users to backup large amounts of data. Tape drives are capable of backing up a couple hundred megabytes to several gigabytes of information without having to spend large sums of money on disks.

Tape Drive Standards

8mm Tape Drive - Manufactured and available through Exabyte 8mm tapes are similar to what are used in camcorder. 8mm tapes are a faster solution then the DAT and transfer up to 6M/Sec. While the tapes are similar to camcorder tapes it is recommended that to backup information you use 8mm tapes designed for your drive.
DAT (Digital Audio Tape) - Digital Audio Tape is primarily developed and marketed by Hewlett-Packard. DAT drives use two types of data formats DDS (Digital Data Storage) and DataDAT. DDS Drives are available in three types DDS-1/2/3. (36-72GB)

DLT (Digital Linear Tape) - DLT drives are a robust and durable medium. The DLT segments the tape into parallel horizontal tracks and records data by streaming the tape across a single stationary head. Released in 1991 DLT drives are very reliable, high-speed, and high-capacity making the DLT drives an excellent use for Network backups. (330-600GB)

AIT - Advance Intelligent Tapes (100-260GB)

Travan- (8GB-20GB)

LTO-Linear Tape Open (200-400GB)
Advance Storage

NAS -Network Attachment Storage

SAN- Storage Area Network

CUPS and Configure in Linux O.S.

CUPS (formerly an acronym for Common Unix Printing System, but now with no official expansion) is a modular printing system for Unix-like computer operating systems which allows a computer to act as a print server. A computer running CUPS is a host that can accept print jobs from client computers, process them, and send them to the appropriate printer.
CUPS consists of a print spooler and scheduler, a filter system that converts the print data to a format that the printer will understand, and a backend system that sends this data to the print device. CUPS uses the Internet Printing Protocol (IPP) as the basis for managing print jobs and queues. It also provides the traditional command line interfaces for the System V and Berkeley print systems, and provides support for the Berkeley print system's Line Printer Daemon protocol and limited support for the server message block (SMB) protocol. System administrators can configure the device drivers which CUPS supplies by editing text files in Adobe's PostScript Printer Description (PPD) format.
CUPS provides a mechanism that allows print jobs to be sent to printers in a standard fashion. The print-data goes to a scheduler which sends jobs to a filter system that converts the print job into a format the printer will understand. The filter system then passes the data on to a backend—a special filter that sends print data to a device or network connection. The system makes extensive use of PostScript and rasterization of data to convert the data into a format suitable for the destination printer.
CUPS offers a standard and modularised printing system that can process numerous data formats on the print server. Before CUPS, it was difficult to find a standard printer management system that would accommodate the very wide variety of printers on the market using their own printer languages and formats. For instance, the System V and Berkeley printing systems were largely incompatible with each other, and they required complicated scripts and workarounds to convert the program's data format to a printable format. They often could not detect the file format that was being sent to the printer and thus could not automatically and correctly convert the data stream. Additionally, data conversion was performed on individual workstations rather than a central server.
CUPS allows printer manufacturers and printer-driver developers to more easily create drivers that work natively on the print server. Processing occurs on the server, allowing for easier network-based printing than with other Unix printing systems. With Samba installed, users can address printers on remote Windows computers and generic PostScript drivers can be used for printing across the network.

Scheduler

The CUPS scheduler implements Internet Printing Protocol (IPP) over HTTP/1.1. A helper application (cups-lpd) converts Line Printer Daemon protocol (LPD) requests to IPP. The scheduler also provides a web-based interface for managing print jobs, the configuration of the server, and for documentation about CUPS itself.

An authorization module controls which IPP and HTTP messages can pass through the system. Once the IPP/HTTP packets are authorised they are sent to the client module, which listens for and processes incoming connections. The client module is also responsible for executing external CGI programs as needed to support web-based printers, classes, and job status monitoring and administration. Once this module has processed its requests, it sends them to the IPP module which performs Uniform Resource Identifier (URI) validation to prevent a client from sidestepping any access controls or authentication on the HTTP server. The URI is a text string that indicates a name or address that can be used to refer to an abstract or physical resource on a network.

The scheduler allows for classes of printers. Applications can send requests to groups of printers in a class, allowing the scheduler to direct the job to the first available printer in that class. A jobs module manages print jobs, sending them to the filter and backend processes for final conversion and printing, and monitoring the status messages from those processes.

The CUPS scheduler utilizes a configuration module, which parses configuration files, initializes CUPS data structures, and starts and stops the CUPS program. The configuration module will stop CUPS services during configuration file processing and then restart the service when processing is complete.

A logging module handles the logging of scheduler events for access, error, and page log files. The main module handles timeouts and dispatch of I/O requests for client connections, watching for signals, handling child process errors and exits, and reloading the server configuration files as needed.

Other modules used by the scheduler include:

• the MIME module, which handles a Multipurpose Internet Mail Extensions (MIME) type and conversion database used in the filtering process that converts print data to a format suitable for a print device;
• a PPD module that handles a list of Postscript Printer Description (PPD) files;
• a devices module that manages a list of devices that are available in the system;
• a printers module that handles printers and PPDs within CUPS.

How to configure printer server in Linux

• 

Linux uses the Common UNIX Printing System, also known as CUPS. CUPS uses the Internet Printing Protocol (IPP) to allow local printing and print sharing. The /etc/cups/ directory stores all the configuration files for printing. However, these files can be easily managed with the Printer Configuration Tool in Linux.

Exam question Raw (Model) printer named printer1 is installed and shared on 192.168.0.254. You should install the shared printer on your PC to connect shared printer using IPP Protocols.

Exam question Raw printer named printerx where x is your station number is installed and shared on server1.example.com. Install the shared printer on your PC to connect shared printer using IPP Protocols. Your server is 192.168.0.254.

Before you can use any printer, you first have to install it on a Linux system on your network. To start the Printer Configuration Tool, go to the System menu on the top panel and select Administration, Printing or execute the commandsystem-config-printer.

If no printers are available for the system, only the Server Settings view is available for selection. If local printers are configured, a Local Printers menu will available.

Install new printer

click New Printer on the toolbar.

In the dialog window that appears, accept the default queue name or change it to a short, descriptive name that begins with a letter and does not contain spaces. Then select printer from list and click on forward and click on finsh.

spool directories
When your system prints a file, it makes use of special directories called spool directories. The location of the spool directory is obtained from the printer's entry in its configuration file. On Linux, the spool directory is located at/var/spool/cups under a directory with the name of the printer.

print job
A print job is a file to be printed. When you send a file to a printer, a copy of it is made and placed in a spool directory set up for that printer.

classes
CUPS features a way to let you select a group of printers to print a job instead of selecting just one. That way, if one printer is busy or down, another printer can be automatically selected to perform the job. Such groupings of printers are calledclasses. Once you have installed your printers, you can group them into different classes.

Once you have successfully installed local printer it will show in right pane. and in left pane you can see all administrative options.

• To view shared printer on other system Tick mark on first option
• To share locally attached printer tick mark on second option
• To allow remote administration of this printer check mark on third option

Tick mark on appropriate option and click on apply

configure window clients

Go on window system and ping from printer server and open internet explorer and give the ip address of server with printer port 631 

This will launch CUPS web application click on manage printer 

now you will see the shared printer on server click on print test page 

A test page will be send on printer server copy this url of printer 

click on start button select printer and fax and click on add new printer. this will launch add new printer wizard clicknext on welcome screen and select network printer

On this screen select internet printer and paste the url which you copied from internet explorer 

Install appropriate driver from list or use have disk option you have drive cd and click next. On next screen set this printerdefaults and click on next and finish. 

Remote administration of print server

Go on linux system and ping from server and click on printing from administration menu

Now click on go to server 

Now give print server ip address 

It will take few minute to connect from server depending on network speed

Now give root password to connect printer server 

you can see all print administrative Manu in right pane Once you have connected with sever 

configure Linux clients

Go on linux system and ping from server and click on printing from administration menu

Now click on new printer 

Click on forward In the next New Printer screen, select the type of connection to internet printing protocols and in hostname give server ip and printer name in printername 

select the appropriate model. If multiple drivers are available, select the one most appropriate for your configuration. If you do not want to choose the default and click forward and finish. The main Printer Configuration window should now include the name of your printer.

To print test page click on print test page and a test page will send to print server 

Managing Printers from the Command-Line

The lpadmin command enables you to perform most printer administration tasks from the command-line.

 lpc To view all known queues
 lpr To send print requests to any local print queue 
 lpq To see the print queue  
lprm To delete the jobs of your choice use it with the job number 
 lp To print any file.