Understanding File Systems and Hard Disk
Objectives:
- Understanding disk drives, hard disk and hard disk interfaces
- Understand Disk Partitions
- Understanding Master Boot Record
- Understanding Different Types of file systems
- Understand various Windows file systems, including FAT and NTFS
- Understand EFS recovery key agent
- Examine registry data
Introduction to File Systems and Hard Disk
This lesson describes file systems and hard disk, two important aspects of data storage. I will begin by giving a general overview of disk drives and then delve deeper into hard drives. I'll then turn away from the discussion of a physical data storage and discusses the various file systems in use on computer systems.
Disk Drive Overview
A disk drive is a mechanism that reads data from a disk and writes data onto a disk. The disk in the disk drive rotates at very high speeds, and heads in the disk drive are used to read and write data.
Different types of disk drives use different types of disks. For example, a hard disk drive (HDD) accesses hard disks, and a floppy disk drive (FDD) accesses floppy disks. An optical disc drive (ODD) reads and writes the data from optical discs.
Types of Disk Drives
Disk drives are categorized into the following types:
• Fixed: These are drives like hard disks, which use media that are not removable.
• Removable: These are drives that use media that are removable. A few examples of removable storage
devices are:
• Floppy disk: This type of drive uses media that are portable magnetic disks on which data and programs can be stored. Floppy disks are disks that are made of either flexible or rigid plastic material. The storage capacity of a floppy disk varies, but typically floppies can hold very little.
CD-ROM: This type of drive uses optical discs. These discs are sturdier than floppy disks, and they can hold more data. Lasers are used to write data to the disc and read data from it. Although CD-ROM discs can only be written to once, other varieties of this optical format can be written to multiple times.
DVD: DVD is an acronym for digital versatile disc. It is a type of optical disc that holds far more information than a CD-ROM. A DVD can hold a minimum of 4.7 GB of data to a maximum of 17 GB.
Zip disk: Zip disks are used to hold data that requires more storage than a floppy disk can provide. Zip disks are used to back up disks and larger documents. Like floppy disks, Zip disks can be written to multiple times.
Different types of disk drives use different types of disks. For example, a hard disk drive (HDD) accesses hard disks, and a floppy disk drive (FDD) accesses floppy disks. An optical disc drive (ODD) reads and writes the data from optical discs.
Types of Disk Drives
Disk drives are categorized into the following types:
• Fixed: These are drives like hard disks, which use media that are not removable.
• Removable: These are drives that use media that are removable. A few examples of removable storage
devices are:
• Floppy disk: This type of drive uses media that are portable magnetic disks on which data and programs can be stored. Floppy disks are disks that are made of either flexible or rigid plastic material. The storage capacity of a floppy disk varies, but typically floppies can hold very little.
CD-ROM: This type of drive uses optical discs. These discs are sturdier than floppy disks, and they can hold more data. Lasers are used to write data to the disc and read data from it. Although CD-ROM discs can only be written to once, other varieties of this optical format can be written to multiple times.
DVD: DVD is an acronym for digital versatile disc. It is a type of optical disc that holds far more information than a CD-ROM. A DVD can hold a minimum of 4.7 GB of data to a maximum of 17 GB.
Zip disk: Zip disks are used to hold data that requires more storage than a floppy disk can provide. Zip disks are used to back up disks and larger documents. Like floppy disks, Zip disks can be written to multiple times.
Hard Disk
Data is organized on a hard disk in a method similar to that of a filing cabinet. The user can easily access the data and programs. When a computer uses a program or data, the program or data is copied from its location to a temporary location. When a user makes changes to a file, the computer saves the file by replacing the older file with the new file. Data is recorded magnetically onto a hard disk. A rapidly spinning platter is used as the recording medium. Heads just above the surface of the platter are used to read data from and write data to the platter. A standard interface connects a hard disk to a computer. Two common interfaces are IDE and SCSI.
Characteristics
Some characteristics that people use to differentiate the various kinds of hard disks include:
Capacity of the hard disk
Interface used
Speed in rotations per minute
Seek time
Access time
Transfer time
Once damaged, a hard disk usually cannot be repaired. When a disk fails, recovering data from it is possible only after installing a new hard disk and accessing the damaged disk as a secondary drive.
Physical Makeup
A hard disk is a sealed unit containing a number of platters in a stack. It can be mounted in a horizontal or vertical position. Electromagnetic read/write heads are positioned above and below each platter. As the platters spin, the drive heads move in toward the center surface and out toward the edge. In this way, the drive heads reach the entire surface of every platter.
On every hard disk, data is stored in thin, concentric bands, called tracks. A drive head reads from or writes to a circular ring called a track. On a 3.5-inch hard disk, there could be a thousand tracks. Tracks consist of sectors, the smallest physical storage units on a hard disk. A sector is almost always 512 bytes (0.5 kilobyte) in size. Figure 1-1 shows the parts of a hard disk.
Zoned Bit Recording
Data is recorded onto a hard disk using a method called zoned bit recording. Zoned bit recording is also known as multiple zone recording (zone recording). In this technique, tracks are combined together into zones depending on their distance from the center of the disk. Each zone is assigned a number of sectors per track.
There are three types of data densities on a hard disk:
• Track density: Space between tracks on a disk
• Area density: Number of bits per square inch on a platter
• Bit density: The bits per unit length of track
Characteristics
Some characteristics that people use to differentiate the various kinds of hard disks include:
Capacity of the hard disk
Interface used
Speed in rotations per minute
Seek time
Access time
Transfer time
Once damaged, a hard disk usually cannot be repaired. When a disk fails, recovering data from it is possible only after installing a new hard disk and accessing the damaged disk as a secondary drive.
Physical Makeup
A hard disk is a sealed unit containing a number of platters in a stack. It can be mounted in a horizontal or vertical position. Electromagnetic read/write heads are positioned above and below each platter. As the platters spin, the drive heads move in toward the center surface and out toward the edge. In this way, the drive heads reach the entire surface of every platter.
On every hard disk, data is stored in thin, concentric bands, called tracks. A drive head reads from or writes to a circular ring called a track. On a 3.5-inch hard disk, there could be a thousand tracks. Tracks consist of sectors, the smallest physical storage units on a hard disk. A sector is almost always 512 bytes (0.5 kilobyte) in size. Figure 1-1 shows the parts of a hard disk.
Zoned Bit Recording
Data is recorded onto a hard disk using a method called zoned bit recording. Zoned bit recording is also known as multiple zone recording (zone recording). In this technique, tracks are combined together into zones depending on their distance from the center of the disk. Each zone is assigned a number of sectors per track.
There are three types of data densities on a hard disk:
• Track density: Space between tracks on a disk
• Area density: Number of bits per square inch on a platter
• Bit density: The bits per unit length of track
Hard Disk Interfaces
- Small computer system interface (SCSI): allows a user to connect 15 peripheral devices to one PCI board known as a SCSI host adapter, which is plugged into the motherboard.
- Integrated drive electronic/enhanced IDE (IDE/EIDE): Connects hard disk drives, optical disk drives and tape drives to personal computers. With this type of interface, the drive controller is built into the drive itself.
- Universal Serial Bus (USB): Connects peripheral devices such as hard disk, modems, printers, digitizer, and data gloves into a computer.
- Advanced technology attachment (ATA): this type of interface comes in two forms: Serial ATA, which provides a point-to-point channel between the mother board and the drive, and Parallel ATA which provides a communications channel between the drive and the computer on which data can travel only one way at a time.
Disk platters are round, flat, magnetic metal or ceramic disk in a hard disk that hold the actual data. It's made form two components: substrate material and magnetic media coating.
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Reference Sites
Review Questions
Directions: Read the overview information on this web page and read the information on the web link above. HWen you have completed this reading, answer the following questions:
- Explain the difference between fixed and removable disk drives, and give at least one example of each.
- Explain zoned bit recording.
- Explain types of hard disk interfaces.
- Explain the difference between serial ATA and parallel ATA
- Describe the composition of a hard disk platter.
- List and describe the file systems most commonly used in Windows
- Explain the Master File Table (MFT) and its contents.
- Describe the functions of the EFS recovery key agent.
- Explain what a partition is, including the different types of partitions.
- List and describe the different tools used to examine the registry.