File systems

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 recreated.

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. 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. 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.

• FAT32 - Created to allow more efficient use of hard drive space and allowed for partitions

up to 8GB using 4KB cluster sizes. 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.

• NTFS4 - NTFS4 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.

• NTFS5 - This is the native file system for Windows 2000. NTFS5 has many new features as

follows:

o Encrypted File System (EFS) - Windows 2000 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.

o Disk Quotas - Provides the ability to set space limitations on users on a per volume

basis.

o Defragmentation - Windows 2000 now includes a disk defragmenter that can be

used on NTFS partitions.

o 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 using dynamic volumes.

o Compression - In Windows 2000 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.

Windows 9x operating systems also employ VFAT which is a protected-mode FAT file system that

prevents DOS and the BIOS from accessing resources. VFAT is the replacement for

SMARTDRV.SYS and uses a driver called VCACHE.

Operating System Supported File Systems

DOS FAT16

Windows 3.x FAT16

Windows 95A FAT16

Windows 95 OSR2 FAT16, FAT32

Windows 98 FAT16, FAT32

Windows 98SE FAT16, FAT32

Windows NT 4 FAT16, NTFS

Windows 2000 FAT16, FAT32, NTFS

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 9x system, a window like the one below will appear.

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.

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 Windows 98 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.

There are several different hard drive utilities that can be found in the various versions of

Windows that are listed below:

• CHKDSK - This utility is run from a DOS prompt and recovers lost allocation units on a

drive that can occur when an application or the system are ended unexpectedly. The /F

switch converts the lost units into a format such that the units can be viewed and deleted.

Can be found in all versions of windows.

• SCANDISK - The ScanDisk utility inspects the hard drive for errors and corrects them.

Scandisk is available in DOS 6.x and Windows 9x.

• DEFRAG - Reorganizes data on the disk for optimal disk performance. In DOS this utility

was run from a DOS prompt. In Windows 9x and 2000 this utility can still be run from a

prompt or can be accessed at Start>Programs>Accessories>System Tools>Disk

Defragementer. Windows NT did not come with a defragmentation utility.

• DRIVESPACE - This utility for windows 9x offers many of the same features as NT's disk

administrator including compression, formatting and drive information.

File Allocation Table (FAT) is a patented[1] file system developed by Microsoft for MS-DOS

and is the primary file system for consumer versions of Microsoft Windows up to and including

Windows Me.

The FAT file system is considered relatively uncomplicated, and is consequently supported by

virtually all existing operating systems for personal computers. This ubiquity makes it an ideal

format for floppy disks and solid-state memory cards, and a convenient way of sharing data

between disparate operating systems installed on the same computer (a dual boot environment).

The most common implementations have a serious drawback in that when files are deleted and new

files written to the media, their fragments tend to become scattered over the entire media making

reading and writing a slow process. Defragmentation is one solution to this, but is often a lengthy

process in itself and has to be repeated regularly to keep the FAT file system clean.

FAT12 FAT16 FAT32

Developer Microsoft

Full Name

File Allocation Table

(12-bit version) (16-bit version) (32-bit version)

Introduced 1977 (Microsoft Disk

BASIC)

July 1988 (MS-DOS

4.0)

August 1996 (Windows 95

OSR2)

Partition identifier 0x01 (MBR)

0x04, 0x06, 0x0E

(MBR)

0x0B, 0x0C (MBR)

EBD0A0A2-B9E5-4433

-87C0-68B6B72699C7 (GPT)

Structures

Directory contents Table

File allocation Linked List

Bad blocks Linked List

Limits

Max file size 32 MiB 2 GiB 4 GiB

Max number of files 4,077 65,517 268,435,437

Max filename size 8.3 or 255 characters when using LFNs

Max volume size 32 MiB 2 GiB

4 GiB with some implementations

2 TiB

Features

Dates recorded Creation, modified, access

Date range January 1, 1980 - December 31, 2107

Forks Not natively

Attributes Read-only, hidden, system, volume label, subdirectory, archive

Permissions No

Transparent

compression

Per-volume, Stacker, DoubleSpace, DriveSpace No

Transparent

encryption

Per-volume only with DR-DOS No

The FAT filesystem uses software methods that had been in use years prior to its

formalization and was created by Bill Gates and Marc McDonald in 1977 for managing disks in

Microsoft Disk BASIC and was incorporated by Tim Paterson in August 1980 to his 86-DOS

operating system for the S-100 8086 CPU boards; the filesystem was the main difference between

86-DOS and CP/M, of which 86-DOS was otherwise mostly a clone.