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A+ Study Guide: Domain 3.0: Operating Systems - File Systems


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Contents:
Introduction
Partitions
File Systems
Managing Drives

Introduction:
In an operating system, the file system is the structure by which files are organized, stored, and named. The file system determines what features and controls you have with regards to the organization, maintenance, and security of your data. Different file systems handle this job differently and vary in the features that they support.

Partitions:
Partitions are configurable logical storage units on your hard drive. Partitions and other storage units, allow you to divide a hard drive in order to better manage the organization of your data and applications. The following are common hard disk configurations.
  • Partition - A partition is a portion of a physical hard disk. A partition can be primary or extended
  • Primary Partition - This is a bootable partition. One primary partition can be made active.
  • Extended Partition - An extended partition is made from the free space on a hard disk and can be broken down into smaller logical drives. There can only be one of these per hard disk.
  • Logical Drive - These are a primary partition or portions of an extended partition that are assigned a drive letter.
  • Volume - This is a disk or part of a disk that is combined with space from the same or another disk to create one larger volume. This volume can be formatted and assigned a drive letter like a logical drive, but can span more than one hard disk. A volume set can be extended without starting over, however to make it smaller, the set must be deleted and re-created.
There are various management tools that can be used to configure drives. The Disk Management MMC is a snap-in for the Computer Management Console in Windows 2000 and XP. You can create partitions, volume sets, logical drives, format disks, etc. NT 4.0 had a similar tool called the "Disk Administrator". DOS and Windows 9x utilize the FDISK utility.

When discussing Windows file systems you need to understand what File Allocation Tables (FAT) are. FAT is a table that an operating system maintains in order to map the clusters (the smallest unit of storage) that a file has been stored in. When files are written to a hard disk, the files are stored in one or more clusters that may be spread out all over the hard disk. The table allows Windows to find the "pieces" of your file and reassemble them when you wish to open it.

File Systems:
Once a drive has been partitioned the way you want, you then need to format it. Formatting is the process that installs the file system on the drive. There are several different types of file systems that are explained below:
  • FAT16 - FAT16 table entries are 16 bits in length limiting hard disk sizes to 2GB. Note that even if the OS supports larger partition sizes, the BIOS must also support logical block addressing (LBA) or the maximum partition that you will be able to create will be either 504 or 528 MB. This file system is no longer used.
  • FAT32 - Created to allow more efficient use of hard drive space. Although the FAT32 file system supports hard disks up to 2 terabytes in size, some hard disks may not be able to contain bootable partitions that are larger than 7.8 GB because of BIOS limitations (must support the INT13 interface). In order to format a drive as FAT32, the "Large disk Support" must be enabled when starting FDISK. FAT32 is not compatible with older versions of Windows including Windows 95A and NT. In Windows 9.x, the CVT1.EXE can be used to convert FAT16 partitions to FAT32.
  • NTFS 4 - NTFS 4 is the file system used by Windows NT that provides increased security and reliability over other file systems. On an NTFS partition, you can't boot from a DOS boot disk - this is one of the security features of NTFS. Additionally, a floppy disk cannot be formatted as NTFS. For this reason it might not be a bad idea to have a small partition formatted FAT so that you can boot into DOS for recovery purposes. In order to convert a FAT partition to NTFS, NT includes a utility called convert.exe.
  • NTFS 5 - This is the native file system for Windows 2000, 2003, and XP. NTFS 5 has many new features as follows:
    • Encrypted File System(EFS) - Windows 2000, 2003, and XP NTFS volumes have the ability to encrypt data on the disk itself. Cipher.exe is a command line utility that allows for bulk or scripted file encryption.
    • Disk Quotas - Provides the ability to set space limitations on users on a per volume basis.
    • Defragmentation - Windows 2000 and XP include a disk defragmenter that can be used on NTFS partitions. Windows NT did not offer this.
    • Volume Mount Points - Provides the ability to add new volumes to the file system without having to assign a drive letter to them. This feature is only available on an NTFS partition.
    • Compression - In Windows 2000 and XP files, folders and entire drives can be compressed by right clicking on the item to be compressed and selecting "properties" and then "advanced".
    The convert.exe utility can be used to convert a FAT or FAT32 partition to NTFS.
  • HPFS - Stands for High Performance File System and is used with OS/2 operating systems. This file system can only be accessed by Windows NT 3.51 and OS/2.
Operating System Supported File Systems
Windows NT 4 FAT16, NTFS
Windows 2000 FAT16, FAT32, NTFS
Windows 2003 FAT16, FAT32, NTFS
Windows XP FAT12, FAT16, FAT32, NTFS

Managing Drives:
In addition to the disk administration utilities previously mentioned, information about a drive can be displayed by right clicking the drive in My Computer or Windows Explorer and selecting "Properties". In a Windows XP system, a window like the one below will appear.

Properties

Here you can view the amount of used and freespace on the drive, the capacity and the file system. The tools tab provides access to defragmentation, scandisk and backup utilities. The Sharing tab is for sharing the drive and setting share-level permissions on it so that it can be accessed across the network. The security tab allows you to configure local file permissions and the quota tab allows you to set disk quotas which limits the amount of disk space that a user can use.

Backing up drives allows you to recover your data or even the entire system if a catastrophe occurs. There are several different types of backup:
  • Full - copies all files and marks them as being backed up.
  • Incremental - copies only files created/changed since last full backup and marks them as being backed up.
  • Differential - copies only files created/changed since last full backup and doesn’t mark them as being backed up.
  • Daily - copies only files created/changed today and doesn’t mark them as being backed up.
In DOS backups can be run with the BACKUP command. There are several switches that can be added to the command.
  • /S - Forces all files and subdirectories to be backed up.
  • /M - Only modified files are backed up.
  • /D - Backs up files modified after a specific date.
  • /T - Backs up files modified after a specific time.
The backup utility can be accessed via Start>Programs>Accessories>System Tools>Backup and also via right clicking on a drive in My Computer and selecting the tools tab as previously mentioned. In Windows 2000/2003/XP, backup can also be launched by entering ntbackup in a "Run" dialogue box.

There are several different hard drive utilities that can be found in the various versions of Windows that are listed below:
  • CHKDSK - Performs the same functions as SCANDISK did in previous Windows versions, but is for Windows 2000/2003/XP.
  • DEFRAG - Reorganizes data on the disk for optimal disk performance. In DOS this utility was run from a DOS prompt. In Windows 2000, 2003, and XP this utility can still be run from a prompt or can be accessed at Start>Programs>Accessories>System Tools>Disk Defragementer.




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