Understanding Hard Drives

Understanding Hard Drives

Hard drives (or fixed disks ) store information magnetically. They are actually made up of rigid cylinders and have a read/write head, much like any other magnetic recording device.

Because hard drives have extremely rigid, durable cylinders, they can spin at very high speeds. This means that the data on the disk can be accessed quickly (definitely faster than floppy drives and most removable media drives). Disk speed (or access time ) is measured in milliseconds and is related to the time it takes a drive to access data. The lower the access time, the faster the drive. For example, an 11ms drive would be faster than a 28ms drive.

We already talked about the different hard drive typesIDE and SCSIin Chapter 3, "Networking Hardware". Regardless of which of these drive types you use, the drive typically has to be partitioned and formatted before you can actually install an operating system or other software onto it. Let's take a look at drive partitions and then the formatting process.

Drive Partitioning

Hard drives come in a variety of sizes. Although plenty of hard drives churning away on networks are not as large as you would think and have less than 10GB of drive space, newer computers boast drives with sizes of in excess of 120 gigabytes (a gigabyte is 1,073,741,824 bytes or 1,024MB). As computer operating systems and network operating systems have become more user friendly and more sophisticated at the same time, the hard drive capacity they need in order to operate has grown dramatically.

While drive capacity has grown, drive price has actually dropped in relation to the amount of storage space that you get for your money. The original 10MB hard drive for the IBM PC cost about the same amount as a 200GB drive you would buy today.

A partition is a logical portion of a hard drive that is actually read by the computer's operating system as a separate drive (see the following note). Therefore, you can have a hard drive with just one partition encompassing the entire space on the drive (the maximum size of a partition can be limited by the file system used) or you can partition a hard drive into several different logical drives.



The maximum size you can make a hard drive partition will depend on the file system you format the drive with. The Mac OS supports disk partitioning and sees it as a way to divide a large storage space into more manageable subsets . Partition sizes on a Mac are not limited, however. In the IBM/compatible PC realm, there are actually three different file systems now available for hard drives: FAT16, FAT32, and NTFS. FAT16 (FAT stands for file allocation table ), the file system used by DOS and early versions of Microsoft Windows, only supports partitions of up to 2GB. With the second release of Windows 95, the FAT32 file system became available. It supplies support for partitions in excess of 2GB (up to 8GB). NTFS (NT File System) can be used on computers running Windows XP and Windows 2000 and provides for partition sizes larger than 2GB. The newest version of NTFS (NTFS 5, available in Windows 2000 Server and Windows Server 2003) also provides an "active disk" format that makes it easier to create and extend partitions on drives.

A number of different tools are available for partitioning drives; on IBM/compatible PCs (which is what we focus on in this chapter) partitions have been created on hard drives since the early days of DOS using a utility called FDISK (see Figure 18.1). FDISK is a DOS command-line utility that provides a menu system used to create and delete partitions on a hard drive. It is available in all the various versions of DOS and Windows.

Figure 18.1. FDISK is a DOS utility used to manage hard drive partitions.


Operating systems such as Windows 2000, XP, and Windows Server 2003 provide GUI utilities that you use to create and manage partitions. For example, Windows Server 2003 provides the Disk Management utility, which allows you to view the various partitions on hard drives (see Figure 18.2). This utility also makes it very easy to create new partitions on a drive.

Figure 18.2. Some operating systems, such as Windows Server 2003, provide a GUI drive-management utility for partitioning and formatting drives.


Drive Formatting

How you format your drive will depend on the operating system you are using. Every operating system offers some type of utility for formatting drives. When you format a drive, you completely remove any data that the drive may have held. Therefore, it's important to be sure you don't need that data before blowing it away.

For example, formatting a drive using a DOS boot disk (such as the installation disk included with versions of Windows such as Windows 9x) is very straightforward. At the DOS command line, you type format C: , where C is the letter of the drive you wish to format.

Formatting a drive is necessary because the appropriate "geography" used by a particular file system for storing and accessing files must be placed on the drive. These areas in which files will be stored are called sectors .



FDISK is included on the boot disk that is provided with the different flavors of Windows, such as Windows 9x (the disk is in the box with the CD). Insert the disk and boot the computer. You can then type fdisk at the command prompt that appears. Once FDISK is up and running, the menu system it provides makes it easy to create any number of partitions on a hard drive. More sophisticated operating systems such as Windows 2000 and XP actually provide you with the ability to create partitions and format them during the installation process.

Most operating systems require that you partition and format at least one drive (in cases where the computer has multiple drives, which is typical for servers) before or during the installation of the operating system. Some operating systems, such as Microsoft Windows XP, also give you the option of changing the partitions on a drive (or drives) and formatting a drive with a different file format during the installation process (such as formatting a FAT drive with the NTFS file system).

Absolute Beginner's Guide to Networking
Absolute Beginners Guide to Networking (4th Edition)
ISBN: 0789729113
EAN: 2147483647
Year: 2002
Pages: 188
Authors: Joe Habraken

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