Transcript File systems: Windows NT versus Linux

File Systems—
NTFS versus Ext2FS
Yingfei Wang
Course: Operating Systems
Instructor: Prof. Anvari
File Management System
A set of system software that provides services to
users and applications in the use of files
Functions:
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Identify and locate the selected file
Directory management
Enforce user access control
Translate user command into file manipulation
commands
Optimize performance
 File allocation, disk scheduling
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File Systems
Windows NT
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NTFS (NT File
System)
Linux

Ext2FS (Second
Extended File System)
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NTFS Structure
Sector
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Smallest physical storage unit on disk
Cluster
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Disk allocation unit for file
Volume
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Disk partition formatted for use by file system
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Ext2FS Structure
Block
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Smallest file allocation unit
Block groups
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Capabilities
NTFS
Ext2FS
Max FS size
2 TB
4 TB
Max file size
4GB – 64GB
2 GB
File name
Up to 255chars
Up to 255chars
Storage size
Variable Cluster fixed block
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Volume Layout of NTFS
Partition boot sector
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Master file table
Boot startup info
Volume layout info
System file
Partition
Boot
sector
Master
File table
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File/folder info
Available space info
File area
System
files
File area
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Master file table
File
MFT
position
Description
location
MFT
0
File for tracking files LCN000
on volume
MFT mirror
1
Metadata copy
…
Log file
2
Transaction record
…
…
…
…
…
User file 1
n
First file, R, …
LCN1668
Directory 1
n+1
First directory
LCN1888
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Physical Layout of Ext2FS
Superblock: contains info about file system
Group descriptor: contains info about each group
Inode: contains info about each file and directory
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Inode Structure
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Number of file system supported
Linux
32
EXT, EXT2, XIA,
MINIX,UMSDOS,
MSDOS, VFAT, HPFS,
SYSV, SMB, etc
NT
3
FAT, NTFS, OS/2
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Virtual File System in Ext2 FS
User process
System call
System calls interface
VFS
Linux
Kernel
DOS FS
Minix FS
Ext2 FS
Buffer Cache
Device Driver
I/O request
Hardware
Disk Controlor
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NTFS
Sorry!
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Security
NTFS
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supports file-level security
Degrees of permissions include R, W, D, P, O
Protection against unauthorized physical access is
better than FAT
Still susceptible to physical access if some utilities
like NTFSDOS is used
Does not support file encryption
EXT2fs
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Supports different levels of security
Can prevent unauthorized access.
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Recoverability
NTFS:
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Use log file to record the changes to volume
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redo or undo
Mirror MFT for back up
Support hot fixing disk sectors
Ext2fs:
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Also offer logging of system transactions
Every block group has a replicated control structure
for backup
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Windows, Linux, Automobiles, etc.
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