Structured File System

1. FAT 16 : This is the 16-bit version of the FAT file system. The 16-bit part describes the way units are allocated on the drive. The FAT16 file system uses a 16-bit number to identify each allocation unit (called cluster), and this gives it a total of 65.536 clusters.

Basic Structure

The FAT16 file system structure contains the following regions:
Region

• Reserved Region (incl. Boot Sector)
• File Allocation Table (FAT)
• Root Directory
• Data Region 

The first sector (boot sector) contain information which is used to calculate the sizes and locations of the other regions. The boot sector also contain code to boot the operating system installed on the volume. The data region is split up into logical blocks called clusters. Each of these clusters has an accompanying entry in the FAT region. The cluster specific entry can either contain a value of the next cluster which contain data from the file, or a so called End-of-file value which means that there are no more clusters which contain data from the file. The root directory and its sub-directories contain filename, dates, attribute flags and starting cluster information about the filesystem objects. 

2. FAT 32 : 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.

3. NTFS : 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.

Formatting a volume with the NTFS file system results in the creation of several system files and the Master File Table (MFT), which contains information about all the files and folders on the NTFS volume.

The piece first information on an NTFS volume is the Partition Boot Sector, which starts at sector 0 and can be up to 16 sectors long. The first file on an NTFS volume is the Master File Table (MFT).

The following figure illustrates the layout of an NTFS volume when formatting has finished.

4. Ext2

1. Ext2 stands for second extended file system.
2. It was introduced in 1993. Developed by Rémy Card.
3. This was developed to overcome the limitation of the original ext file system.
4. Ext2 does not have journaling feature.
5. On flash drives, usb drives, ext2 is recommended, as it doesn’t need to do the over head of journaling.
6. Maximum individual file size can be from 16 GB to 2 TB
7. Overall ext2 file system size can be from 2 TB to 32 TB

If you want to create the partition of Ext2, you can use the command 

mke2fs /dev/sda1

5. Ext3

1. Ext3 stands for third extended file system.
2. It was introduced in 2001. Developed by Stephen Tweedie.
3. Starting from Linux Kernel 2.4.15 ext3 was available.
4. The main benefit of ext3 is that it allows journaling.
5. Journaling has a dedicated area in the file system, where all the changes are tracked. When the system crashes, the possibility of file system corruption is less because of journaling.
6. Maximum individual file size can be from 16 GB to 2 TB
7. Overall ext3 file system size can be from 2 TB to 32 TB
8. There are three types of journaling available in ext3 file system.
   1. Journal – Metadata and content are saved in the journal.
   2. Ordered – Only metadata is saved in the journal. Metadata are journaled only after writing the content to disk. This is the default.
   3. Writeback – Only metadata is saved in the journal. Metadata might be journaled either before or after the content is written to the disk.
9. You can convert a ext2 file system to ext3 file system directly (without backup/restore).

If you want to create the file system of Ext3, you can use the command

mkfs.ext3 /dev/sda1
or you can use
mke2fs -j /dev/sda1