Hard Disk

Partitions created on a basic disk are called basic volumes. An administrator can create more than one basic volume by partitioning the hard disk for the purpose of organizing the files and folders or supporting multiple operating systems on a single hard disk.

On a basic disk, three types of partitions can be created, namely primary, extended, and logical. An administrator can configure a maximum of four primary partitions on a computer running the Windows XP operating system. Although the administrator can configure any of the created primary partitions as an active or bootable partition, he can view only one primary partition with a drive letter at a time since only one primary partition is active at a time. Other primary partitions are invisible and are not assigned a drive letter. An extended partition allows administrators to exceed the limit of primary partitions that can be created on a hard disk. An extended partition serves as a shell in which a user can create unlimited logical partitions. Logical partitions are visible and generally used to organize files.

In addition to the basic disk, Windows XP Professional also supports the dynamic disk, which overcomes the limitations of the basic disk. Dynamic disks are actually physical disks that are created and managed with the Disk Management utility in Windows XP. Dynamic disks provide several new features that cannot be performed on basic disks. Dynamic disks do not use partitions or logical drives. Instead, they use dynamic volumes to subdivide physical disks into one or more drives. Three types of dynamic volumes can be created on a Windows XP-based computer, namely simple, spanned, and striped.

1. Simple volumes: Simple volumes contain disk space from a single hard disk and can be extended, if required.
2. Spanned volumes:Spanned volumes combine areas of unallocated space from multiple disks into one logical volume. Such volumes allow a user to efficiently use all the hard disk space and drive letters on a multiple-disk system. Spanned volumes contain disk space from two to thirty-two disks with varying amount of disk space from each disk. When a user needs to create a volume but does not have enough free space on a single disk, he can create the volume by combining sections of unallocated space from multiple disks into one spanned volume. Spanned volumes are fault-intolerant, which means that all the data in the entire spanned volume is lost if any of the disks containing the spanned volume fails. When Windows writes data to a spanned volume, it writes to the area on the first disk until the whole area is filled, then to the area on the second disk, and so on until the maximum limit of thirty-two disks is reached. Existing spanned volumes formatted with the NTFS file system can be extended by increasing the capacity of an already existing volume. However, after extending a spanned volume, a user cannot delete any portion of it without deleting the entire spanned volume. Therefore, the users are advised to back up all the information on the volume before making any changes to the spanned volumes.
3. Striped Volumes:Striped volumes are created by combining areas of free space on two or more disks into one logical volume. Like spanned volumes, striped volumes also contain disk space from two to thirty-two disks. But unlike spanned volumes, striped volumes require a user to use an identical amount of disk space from each hard disk. When Windows stripes data to the striped volume, it divides the complete data in multiples of 64KB and writes to the disk in a fixed order. The whole data is divided into blocks and spread in a fixed order among all the disks in the array. For example, a 256MB file is divided into four 64KB files and each one is stored on a separate disk. Like spanned volumes, striped volumes are also fault-intolerant and cannot be extended or mirrored. Striped volumes use RAID-0, which stripes data across multiple disks. This is why they are also referred to as RAID 0. Despite their lack of fault tolerance, striped volumes improve the performance by increasing I/O performance and distributing I/O requests across disks. Striped volumes cannot be supported by MS-DOS, Windows 95, Windows 98, Windows Me, Windows NT 4.0, Windows XP Home Edition, and other operating systems that do not support dynamic storage capability.
   Windows XP uses the Disk Management tool to create and manage volumes on fixed and removable disks. This can be accessed from within the Computer Management window as shown in the following figure:

Using the Disk Management tool, a user can manage the hard disk very effectively. He can create primary, extended, as well as logical partitions. It is necessary to format a volume to let it accept data. By using Disk Management, a user can format volumes, assign drive letters to the formatted volumes, and change the default drive letters. He can choose a file system for a particular volume and configure the default cluster size for any of the file systems. By using Disk Management, users can also enable file and folder compression on NTFS volumes.

Windows XP allows mounting of volumes by using a path instead of assigning a drive letter. Mounted volumes allow administrators to extend the available space on an existing volume without extending the actual size of the volume. Administrators can create multiple volume mount points for a particular volume. Using Disk Management, administrators can add volume mount points to an existing volume.

Windows XP Professional also allows administrators to avail of the features of dynamic disks by converting the basic disks to dynamic disks without losing the existing data. By using Disk Management, different dynamic volumes can be created and managed. As we know that dynamic disks are not supported by all the operating systems, it becomes necessary to use the basic disks. Windows XP Professional provides a feature to accomplish this. It can be used to revert from dynamic disk to the basic disk.

Another feature that Windows XP Professional supports is extending volumes on both basic as well as dynamic disks. On basic disks, it can be accomplished by running the DISKPART command-line utility and on dynamic disks, either by using the Disk Management tool or the DISKPART command.

Extensions of primary partitions and logical drives on basic disks require the following conditions to be fulfilled:

• The volume must be formatted with the NTFS file system.
• The volume is extended on the same hard disk. Volumes on basic disks cannot be extended to include disk space on another hard disk.
• The volume must not be a system or boot volume. Such volumes cannot be extended.

A volume can be extended by running the DISKPART utility from the command line, by selecting the volume, and then by executing the following command:

EXTEND [SIZE=N] [NOERR]

On dynamic disks, simple volumes formatted with only the NTFS file system can be extended by attaching additional unallocated space from the same disk or from a different disk. Unlike basic disks, space on dynamic disks need not be contiguous.

Moving Disks: Windows XP Professional enables administrators to install disks into another computer that is using the operating system that supports the dynamic disk feature. Moving disks to other computers proves to be very useful in case a computer fails and the hard disk is still functional.
Windows XP allows managing disk-management tasks by running the DISKPART command from the command prompt and creating scripts for automating the frequently performed tasks.

Windows XP provides several efficient disk maintenance features such as the CHKDSK, DISK DEFRAGMENTER, and DISK CLEANUP utilities. The CHKDSK command is used to verify and repair the integrity of the file system on a volume. Defragmentation is a process of rearranging the several pieces of files and folders on the disk into contiguous spaces. Disk Defragmenter, a maintenance tool, supported by Windows XP, enables a user to defragment a hard disk and consolidate the free space on the hard disk. This improves the performance of the computer to a great extent. Windows XP also provides a command-line version of the Disk Defragmenter utility, called the DEFRAG.EXE command, which can be used to perform all the maintenance tasks that Disk Defragmenter does. When the hard disk of a computer is becoming low on available space, then a user can delete unnecessary files (such as Temporary Internet files, Temporary Offline files, Recycle Bin, etc.) by using the DISK CLEANUP utility to increase the available free space.

In the end, we can conclude that Windows XP Professional and Home Edition, with their advanced disk management and maintenance features, facilitate the administrators effectively in performing their tasks. It is for this and many other reasons that Windows XP is being used to a great extent in many large organizations.

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