Structure File System

• FAT16

FAT16 is a file system that uses the allocation unit that has a limit of up to 16-bit, so it can store up to 216 units of allocation (65536 pieces). This file system has a capacity limit of up to 4 Gigabyte sizes only. Allocation unit size used by the FAT16 partitiondepends on the capacity that was about to be formatted: if the partition size is less than 16 megabytes, then Windows will use the FAT12 file system, and if the partition sizelarger than 16 megabytes, then Windows will use the FAT16 file system. The following table contains information any operating system that supports the FAT16 file system.

• FAT32

FAT32 uses allocation unit size is smaller than the file system FAT12/FAT16, so FAT32is more efficient when applied on a large partition (size greater than 512 Megabytes).The savings made ​​by comparison with FAT16/FAT12 FAT32 is approximately 20% to 27%. Windows 98 has a utility that can be used to convert the FAT16 partition to FAT32without losing data.

FAT32 is a derivative of the File Allocation Table (FAT) file system that supports drives with over 2GB of storage. Because FAT32 drives can contain more than 65,526 clusters, smaller clusters are used than on large FAT16 drives. This method results in more efficient space allocation on the FAT32 drive.
The largest possible file for a FAT32 drive is 4GB minus 2 bytes.
The FAT32 file system includes four bytes per cluster within the file allocation table. Note that the high 4 bits of the 32-bit values in the FAT32 file allocation table are reserved and are not part of the cluster number.

• THE FAT FILE SYSTEMS. FAT32 FAT16 FAT12

The File Allocation Table (FAT) file system is a simple file system originally designed for small disks and simple folder structures. The FAT file system is named for its method of organization, the file allocation table, which resides at the beginning of the volume. To protect the volume, two copies of the table are kept, in case one becomes damaged. In addition, the file allocation tables and the root folder must be stored in a fixed location so that the files needed to start the system can be correctly located.

A volume formatted with the FAT file system is allocated in clusters. The default cluster size is determined by the size of the volume. For the FAT file system, the cluster number must fit in 16 bits and must be a power of two.

Structure of a FAT Volume

The figure below illustrates how the FAT file system organizes a volume

• NTFS

NTFS supports multiple data streams, where the stream name identifies a new data attribute on the file. A handle can be opened to each data stream. A data stream, then, is a unique set of file attributes. Streams have separate opportunistic locks, file locks, and sizes, but common permissions.

Master File Table and Metadata
When a volume is formatted with NTFS, a Master File Table (MFT) file and other pieces of metadata are created. Metadata are the files NTFS uses to implement the file system structure. NTFS reserves the first 16 records of the MFT for metadata files
The data segment locations for both $Mft and $MftMirr are recorded in the boot sector. If the first MFT record is corrupted, NTFS reads the second record to find the MFT mirror file. A duplicate of the boot sector is located at the end of the volum
Table   3.5 Metadata Stored in the Master File Table

System File	File Name	MFT Record	Purpose of the File
Master file table	$Mft	0	Contains one base file record for each file and directory on an NTFS volume. If the allocation information for a file or directory is too large to fit within a single record, other file records are allocated as well.
Master file table 2	$MftMirr	1	A duplicate image of the first four records of the MFT. This file guarantees access to the MFT in case of a single-sector failure.
Log file	$LogFile	2	Contains a list of transaction steps used for NTFS recoverability. Log file size depends upon the volume size. It is used by Windows 2000 to restore consistency to NTFS in the event of a system failure. For more information about the log file, see "NTFS Recoverability" later in this chapter.
Volume	$Volume	3	Contains information about the volume, such as the volume label and the volume version.
Attribute definitions	$AttrDef	4	A table of attribute names, numbers, and descriptions.
Root file name index	$	5	The root directory.
Cluster bitmap	$Bitmap	6	A representation of the volume showing which clusters are in use.
Boot sector	$Boot	7	Includes the bootstrap for the volume if it is a bootable volume.
Bad cluster file	$BadClus	8	Contains bad clusters for the volume.
Security file	$Secure	9	Contains unique security descriptors for all files within a volume.
Upcase table	$Upcase	10	Converts lowercase characters to matching Unicode uppercase characters.
NTFS extension file	$Extend	11	Used for various optional extensions such as quotas, reparse point data, and object identifiers.
		12–15	Reserved for future use.

• EXT2

EXT2 is a powerful file system in linux. EXT2 is also one of the most powerful file systemand the foundation of all linux distributions. In the EXT2 file system, file data is stored as data blocks. This block of data has the same length, and although the length variesbetween EXT2 file system, a large block is determined when the file system is createdwith the command mk2fs. If a large block is 1024 bytes, then a large file with 1025 byteswill be wearing two blocks. This means that we throw away a half a block per file.
EXT2 defines the file system topology by providing the sense that every file on the system diasosiasiakan the inode data structure. A shows the block where the inode in afile on every file access rights, file modification time, and file type. Each file in the EXT2file system consists of a single inode and each inode has a unique identification number. Inode inode-stored in the file system inode table. Directory in the EXT2 filesystem is a special file that contains a pointer to the inode of each directory content


XT2 first developed and integrated in the Linux kernel, and is now also being developedfor use on other operating systems.
The goal is to create a powerful file system, which can implement those files from UNIXsemantics, and has an advanced service features.

• abilities:

Ext2 file system capable of supporting multiple file types from UNIX standard, such asregular files, directories, device special files and symbolic links.
Ext2 able to manage system files are created in a large partition.
Ext2 file system capable of generating file names are long. Maximum of 255 characters.
Ext2 require several blocks to super user (root).

• Ext3

Ext3 is a journalled file system, journalled file system designed to help protect data in it.With a journalled filesystem, then we no longer need to check the consistency of data,which will take very long for my disk.

Ext3 is a filesystem that was developed for use on the Linux operating system. Ext3 is the result of improvement of Ext2 Ext2 into better shape by adding a variety ofadvantages.

• Pros:

Ext3 does not support the process of checking the file system, even when the system isnot cleaned experiencing "shutdown", except in some very rare hardware errors.
Things like this happen because the data is written or stored into a disk in a way so that the file system is always consistent.
The time required to recover EXT3 file system after the system is not cleaned off
Is independent of the size of the file system or file number, but depends on the size of the "journal" used to maintain consistency. Journal of the size of the initial (default)
Requires about 1 second to recover (depending on the speed of hardware).

• Ext2 and Ext3 comparison:

In general, the principles of the Ext2 with Ext3.
Method of accessing files, data security, and the use of disk space between the filesystem is almost the same.
The fundamental difference between the two file systems is the concept of journaling file system that is used in Ext3.
This led to the concept of journaling Ext2 and Ext3 have differences in terms of durabilityand data recovery from damage.
This led to the concept of journaling Ext3 Ext2 is much faster than the recovery of datadue to damage.