Master Boot Record (MBR) is the information in the first sector of each hard disk or diskette that identifies how and where the operating system is in place that can boot (loaded) into the computer's main storage or random access memory.
Master Boot Record is also sometimes called a "partition sector" or "master partition table" because it includes a table that puts any hard disk partition that has been formatted into. In addition to this table, the MBR also includes a program that reads the boot sector of partition record that contains the operating system will boot into RAM. In turn, the record contains a program that loads the rest of the operating system into RAM.
Master Boot Record is also sometimes called a "partition sector" or "master partition table" because it includes a table that puts any hard disk partition that has been formatted into. In addition to this table, the MBR also includes a program that reads the boot sector of partition record that contains the operating system will boot into RAM. In turn, the record contains a program that loads the rest of the operating system into RAM.
structure file system:
- FAT (file allocation Table)FAT or FAT16 is known by the name of a file system used by MS-DOS and WINDOWS to manage file storage.
File Allocation Table is a data structure created by Windows when you format a volume by using FAT or FAT32 file system. Windows stores information about each file in the FAT so that it can menfambill file at a later time.
FAT32 is a derivative of FAT16. FAT32 supports smaller cluster sizes and larger volumes than FAT16.
The difference between FAT16 to FAT32.
FAT 16:
- Max size of 4 Gigabyte filer
- Max number of files 268 435 437
- Max length of file names 255
- Max size of partition 2 Gigabyte
- Have the file permissions
FAT 32:
- Max size of 4 Gigabyte filer
- Max number of files 65 517
- Max length of file names 255
- Max size of partition 2 Terabyte
- Have the file permissions - NTFS (new technology file system)NTFS is an advanced partition systems that provide the performance security, reliability, and features that can not be found in the FAT version.
For example:
- NTFS guarantees volume consistency by using standard transaction records and recovery techniques.
- If the system fails, NTFS uses file records and checkpoint information to restore the consistency of the file system.
- NTFS also provides features such as file and folder permissions, encryption, disk quotas, and compression.
- In this large file system partition while max 256 Terra Byte 16 Terra Bytes of data.
In terms of security of NTFS file security application allows the level of giving NTFS permissions, so that we can control which users have access to a file type where.
Security can be given at two different levels
1. only users
2. in group :Network File System (NFS)
NTFS is already in all the windows of the 2000, XP, Vista. And uses 64-bit address and supports disk partitions up to 264. - The second extended file system (ext2)Both the Extended File System is designed as an extensible and robust file system for Linux. It is also the most successful file system so far in the Linux community and is the basis for all currently shipping Linux distributions.
Data structure in EXT2:
Space is divided into blocks in ext2. And the blocks are grouped into block groups, analogous to the cylinder in the unix file system.
Each block group contains a copy of the superblock and block group table description, and all of the blogs contain the block bitmap, an inode bitmap mode table and finally the actual data blocks.
The superblock contains important information that is critical to the operation darisistem boot, so the backup copy is created in the block number in the file system. However, usually only the first copy, which is found in the first block of the file system, used in the boot.
Group descriptor stores the location of the block bitmap, inode bitmap and the beginning of the inode table for every block group and this, in turn stored in a group descriptor table.inode:
Each file or directory is represented by the inode. This includes data on the inode size, permissions, ownership, and location on the disk from a file or directory.
Example ext2 inode structure:Quote of the linux kernel documentation to ext2:
There is a pointer to the first 12 blocks containing the data file in the inode. There is a pointer to indirect block (which contains a pointer to the next set of blocks), a pointer to a block of double indirect trebly indirect pointer to the block.
So, there are structures in the 15-pointer ext2, for the first 12 are direct block. Pointer number 13 points to an indirect block, double block number 14 to number 15 and not directly to the trebly indirect block.Disadvantages of EXT2:
A. Limit 32 768 level sub directory
2. Can not handle files larger than 2TB
3. Block size is limited by the architecture - The third extended file system (ext3)ext3 or third extended filesystem is a journaled file system used by the Linux kernel. Although its performance (speed) is less attractive than competing Linux filesystems like ext4, JFS, ReiserFS and XFS, it has a significant advantage in that it allows on-site upgrade of the ext2 file system without having to back up and restore data. Benchmarks show that Ext3 also uses less CPU power than ReiserFS and XFS. because it is considered safer.
advantages of ext3:
- A journaling file system created to help protect data in it.
- Online file system growth
- Htree indexing for larger directoriesshortage:
- function:
ext3, can not fsck-ed while the filesystem is mounted for write. Try to check the file system is mounted may detect false errors where data modified disk has not been reached yet, and damage the file system in an attempt to "fix" this error.
- recovery:
No support recovery of deleted files in file system design. The active ext3 driver to wipe deleted files inode file for crash safety reasons.
- Lack of support snapshot:
ext3 does not have native support for snapshots - the ability to quickly grasp the state of the filesystem at an arbitrary time, instead of relying on less space-efficient snapshot volume level provided by the Linux LVM. The Next3 file system is a modified version of ext3 that offers support for images, but still compatibility to ext3 on-disk format.
- There is no checksum in the journal
Ext3 does not do checksumming when writing to the journal. If barrier = 1 is enabled as a mount option (in / etc / fstab), and if the hardware is doing out-of-order write caching, one runs the risk of severe filesystem corruption during a crash.my resorce: www.dewassoc.com
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