Presented to: Sir Ahmad Karim

Presented by: Tahmina Gillani (MIT-08-13) Mehwish saba (MIT-08-03) Hira Nargis (MIT-08-19) Misbah Fatima (MIT-08-12) Ayesha Raee (MIT-08-04)

FILE SYSTEMS

File Names

1 to 255 characters in lengthThis includes the path

You can use uppercase and lowercase (case-aware, but not case-sensitive)

You can use spaces and periods You cannot use these characters:

/ \ : * ? “ < > |

File Names continued

Filenames consist of two parts Main part of filename

Identifies the contents of the file

File extension Identifies the file type

The last period separates the file extension from the main part of the filename.

Windows typically associates a file extension with an application installed on a computer

Folder Names

Folder names follow the same guidelines for naming files

Folder names usually do not have a file extension

MS-DOS filename

Filename: 1 to 8 characters File extension: 1 to 3 characters DOS only uses uppercase You cannot use spaces A single period separates the file extension from

the filename You cannot use these characters:

/ \ : * ? “ < > | + = ; , [ ]

The Full Path

What does it mean?The complete path from the root of the files

system to the desired object.

Use \ (vs. /)C:\ - the root

C:\documents and settings\theresa\octc\cis110\filesystems.ppt

File Systems

A file system defines the structure and the rules used to read, write, and maintain information stored on a disk.

Which system used is determined by;HardwareSoftwareSecurity needsNeed for a dual-booting system

FAT???

file allocation table – where the OS records how the disk space is used

File Systems FAT 16 – oldest, created for DOS, supported by

most OSs’, cannot be installed on partitions larger than 2 GB, or on hard drives larger than 4GB.

FAT 32 – supports disks from 512 to 2TB, compatible with Windows 98 and up

NTFS – (new technology file system) – better file security (Encrypting File System), disk compression, logging features, reliability and stability. NTFS volumes can not be accessed by DOS, or Windows 95 or Windows 98.

File Systems

The operating system keeps track of data (documents, pictures, etc.) by placing it into a file.

To store and retrieve files: Disk divided into tracks Tracks are divided into sectors Sectors grouped into clusters

Number of sectors in a cluster is determined bySize of the hard driveFile allocation system – FAT, FAT32, NTFS

Tracks

Sectors within a

Track

Cluster

A hard disk has extremely smooth metal or glass plates called “platters” (vs. the floppy mylar disk of a floppy disk).

Each platter is divided into tracks and sectors by the format operation, like a floppy disk, however the number of tracks and sectors is different. The number of tracks on a hard disk depends on the disk size and the manufacturer.

A cluster, also known as an allocation unit, consists of one or more sectors of storage space, and represents the minimum amount of space that an operating system allocates when saving the contents of a file to a disk.

The number of sectors per cluster is dependent on Type of disk (floppy disk, hard disk) Version of operating systems Size of disk

Every sector contains 512 bytes. (NTFS does allow you to change this number.)

The number of clusters per disk is determined by the filing system (FAT 16, FAT 32 or NTFS).

Clusters?

DRIVE SIZEFAT 16

Cluster SizeFAT 32

Cluster SizeNTFS

Cluster Size

260 to 511 MB 8 KB (16 sectors) Not Supported 512 bytes (1 sector)

512 to 1023 MB 16 KB (32 sectors) 4 KB (8 sectors) 1KB (2 sectors)

1024 MB to 2 GB 32 KB (64 sectors) 4 KB (8 sectors) 2 KB (4 sectors)

2 to 4 GB 64 KB (128 sectors) 4 KB (8 sectors) 4 KB (8 sectors)

4 to 8 GB Not Supported 4 KB (8 sectors) 8 KB (16 sectors)

8 to 16 GB Not Supported 8 KB (16 sectors) 16 KB (32 sectors)

16 to 32 GB Not Supported 16 KB (32 sectors) 32 KB ( 64 sectors)

>32 GB (up to 2 TB) Not Supported 32 KB (64 sectors) 64 KB (128 sectors)

So, what does this all mean to us, as Windows XP users?

The bigger your disk – the bigger your clusters (because there is a maximum number of clusters per disk).

One way to help alleviate the problem of slack space is to partition the hard drive into smaller “drives”. Reducing the drive size will reduce the cluster size.

Which file system should you use?

If your computer runs only Windows XP and you do not plan to install other OS, use NTFS

However if you want to use other OS and you want to access the volumes you must use FAT16 or FAT32

OS and File System Compatibility

Operating System FAT16 FAT32 NTFS

Windows XP

Windows 2000

Windows NT

Windows 95, 98, ME

Windows 95

MS-DOS

What happens during the Formatting Process?

OS creates four tables in the 1st sectorsBoot Record – the name & version number of the OS, info. Master File Table #1- keeps track of

Available clustersClusters that contain dataClusters that are defectiveClusters that contain OS files

Master File Table #2 – copy of MFT #1Directory Table – top level folder and file information

Formatting Process, cont.

Full Format lays down new tracks and sectorsVerifies the integrity of each sector

By doing a surface scan – OS will put dummy data into sectors and then try to read the sector

Quick FormatRemoves filesDoes not check for defective sectors

Ext 3

Ext 3(third extended file system): Journaled file system used by Linux kernel. Introduced November 2001(Linux 2.4.15) Enhanced form of Ext 2 which Improve reliability Eliminates the need to check the file

system after an unclean shut down.

Advantages

Back up and restore data Less CPU power than other file systems in

Linux like XFS. More safer due to its relative simplicity and

wider testing base.

Cont’d

The ext3 file system adds, over its predecessor:

A journaling file system. Online file system growth. Htree indexing for larger directries.

Cont’d

Size limits: Maximum size for both indiviual files and

entire file systems. Max file size 16 GB – 2 TB. Max number of files:Variable,Allocated at

creation time. Max file name length:254 Bytes.

Journalling levels

Three levels in Linux implementation of Ext 3:

Journal(lowest risk) Ordered(medium risk) Writeback(highest risk)

Disadvantages

Functionality Defregmentation Recovery Compression NO checksumming in journal

Thanks for your

kind presence