File System Structured

FAT (File Allocation Table) system is a file system that uses a file allocation table structure as the way he operates. 

FAT 16 is a file system that use allocation unit have limit until 16-bit. so can save unit allocation until 65536. This file system has a capacity limit of up to 4 Gigabyte sizes only. Allocation unit size used by the FAT16 partition depends 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 size larger than 16 megabytes, then Windows will use the FAT16 file system.  below is layout of FAT16

FAT 32 is a file system that use allocation unit have limit until 32-bit. The maximum allocation unit size can reach 32 768 bytes (64 sectors), so that theoretically can put 8 terabytes (8192 gigabytes),below is layout of FAT16

NTFS (New Technology File System) is the standard file system of windows NT,The Windows NT file system (NTFS) provides a combination of performance, reliability, and compatibility not found in the FAT file system. It is designed to quickly perform standard file operations such as read, write, and search - and even advanced operations such as file-system recovery - on very large hard disks.The NTFS file system is based on a different structure, called a master file table, containing records about the files and directories of the partition. The first record, called a descriptor, contains information on the MFT (a copy of it is stored in the second record). The third record contains the log file, a file containing all actions performed on the partition. The following records, making up what is known as the core, reference each file and directory of the partition in the form of objects with assigned attributes. This means that the information concerning each file is stored in a file, which is itself registered inside the MFT. The MFT is therefore a storage structure of the data in the partition, and not a list of clusters.

EXT2 are file system created for linux. EXT2 can manage data in big partitions. Overall ext2 file system size can be from 2 TB to 32 TB. like a lot of the file systems, EXT2 built on the premise that the data held in files is kept in data blocks. These data blocks are all of the same length and, although that length can vary between different EXT2 file systems the block size of a particular EXT2 file system is set when it is created.Every file's size is rounded up to an integral number of blocks. If the block size is 1024 bytes, then a file of 1025 bytes will occupy two 1024 byte blocks. EXT2 defines the file system topology by describing each file in the system with an inode data structure. An inode describes which blocks the data within a file occupies as well as the access rights of the file, the file's modification times and the type of the file. Every file in the EXT2 file system is described by a single inode and each inode has a single unique number identifying it. The inodes for the file system are all kept together in inode tables. EXT2 directories are simply special files (themselves described by inodes) which contain pointers to the inodes of their directory entries.

EXT2 filesystem is made up of block groups. Physical Layout of the EXT2 File system as below :

the layout of the EXT2 file system as occupying a series of blocks in a block structured device. So far as each file system is concerned, block devices are just a series of blocks which can be read and written. A file system does not need to concern itself with where on the physical media a block should be put, that is the job of the device's driver. Whenever a file system needs to read information or data from the block device containing it, it requests that its supporting device driver reads an integral number of blocks. The EXT2 file system divides the logical partition that it occupies into Block Groups.   Each group duplicates information critical to the integrity of the file system as well as holding real files and directories as blocks of information and data. This duplication is neccessary should a disaster occur and the file system need recovering. The subsections describe in more detail the contents of each Block Group. 

EXT3 is the development of EXT2, but EXT3 include Journaling :

• Journal - Metadata and content are saved in the journal.
• Ordered - Only metadata is saved in the journal. Metadata are Journaled only after writing the content to disk. This is the default.
• Writeback - Only metadata is saved in the journal. Metadata Might Be Journaled either before or after the content is written to the disk.