What does a file system do?

Transcription

1 System files

2 What does a file system do? A file system is a method for storing and organizing computer files and the data they contain to make it easy to find and access them. File systems exist on hard drives, pen drives, cd s, dvd s and any other form of data storage medium Most data storage devices have array of fixed-size blocks, sometimes called sectors, and file system is in charge of organizing these sectors into files and directories. It is also in charge of indexing the media so it knows where and what each file is 2

3 Types of File Systems Disk file systems FAT (File Allocation Table), NTFS, HFS (Hierarchical File System), ext2, ext3, ISO9660 and UDF FAT(FAT12, FAT16, FAT32), and especially NTFS are primarily used on Windows operating systems. FAT is also the standard file system for floppy drives and is still used today HFS is used by Mac OS, and ext2, ext3 are used on various linux operating systems ISO9660 and UDF are used on optical media 3

4 What OS Support (for FAT/NTFS) In general, systems that can support NTFS also support FAT WinNT, Windows 2000, and WinXP support both FAT and NTFS. On the other hand, older versions of Windows only support FAT (Win95, Win98, me) 4

5 FAT FAT gets its name form the file allocation table stored near the beginning of the drive FAT16 is a 16-bit file system FAT32 is a 32-bit file system The only option if a partition needs to be used for dualbooting with another O/S (e.g. DOS, Win 9x, etc.) 5

6 FAT 16 Used by MS-DOS Traditionally limited to partitions up to 2 GB out of date maximum partition size 2 GB Appropriate for very small hard-disk partitions only Limitations Small partition sizes No file system security features Disk space usage is poor Don t use it unless you have to use really old applications or operating systems 6

7 FAT 32 A derivative of the FAT16 file system Because is a 32-bit file system it can address more clusters than FAT16 It also means FAT32 can support larger partitions Supports partition sizes up to 2 TB Still does not provide advanced security features Cannot configure permissions on file and folder resources 7

8 NTFS Introduced with Windows NT operating system Windows NT 4.0 Windows 2000 Windows XP Windows Server 2003 Theoretically supports partition sizes of up to 16 Exabyte (EB) Practically supports maximum partition sizes from 2 TB to 16 TB 8

9 NTFS Native Windows file system. Can only be read by NT, Win2K and Windows 2003/XP OS. Supports file/folder compression. Larger disk/partition/file support. Built-in file/folder security. Fault-tolerance support (RAID) NTFS5 has addt l features of dynamic volumes, disk quotas, encryption (EFS), FAT32 support More efficient for larger disk/partitions over 500MB, especially over 2GB. Can combine multiple physical disks under 1 driver letter 9

10 Important features NTFS 10 Supports volumes up to 2 TB in size Compression Security Encryption

11 What does NTFS offer? NTFS offers what FAT does not: Performance Reliability Compatibility It was designed to quickly perform standard file operations as: Reading Writing Searching...and File system recovery on very large hard disks 11

12 Disadvantages of NTFS It is not recommended to use NTFS on a volume that is smaller than approximately 400 MB Currently, there is no file encryption built into NTFS It is not possible to format a floppy disk with the NTFS file system 12

13 FAT vs. NTFS FAT will still exist in mobile and small storage devices, but NTFS more likely for Windows NTFS is more complex and more scalable FAT retrieves a file by searching the chain of allocation units directory entries, NTFS finds files more directly 13

14 NTFS v. FAT32 Disk Formats Use NTFS unless you have to use FAT32 Compatibility Windows 95/98/Me cannot recognize NTFS volumes 14 On multiboot systems, you must use FAT32 for any local drives that you want to access when you boot the system using Windows 95, Windows 98, or Windows Me

15 NTFS v. FAT32 Disk Formats 15 Security NTFS permissions and encryption are not available on FAT or FAT32 partitions

16 Reliability NTFS v. FAT32 Disk Formats An NTFS volume can recover from disk errors more readily than an otherwise identical FAT/FAT32 drive NTFS uses log files to keep track of all disk activity NTFS can mark bad clusters and stop using them 16

17 Expandability NTFS v. FAT32 Disk Formats NTFS-formatted volumes can be expanded without having to back up, repartition, reformat, and restore (if you use Dynamic Disk) 17

18 Efficiency NTFS v. FAT32 Disk Formats On partitions greater than 8 GB in size, NTFS volumes manage space more efficiently than FAT32 The maximum partition size for a FAT32 drive created by Windows XP is 32 GB With NTFS, a volume can be up to 16 terabytes (16,384 GB) 18

19 Compare FAT & NTFS FAT 19 NTFS Support by DOS, OS/2, Windows 95, and Window NT(Should be used if you need to Dual-boot and access the partition from another OS) No local security available Does not support Macintosh files Only supported under the NT OS Local security is available Support Macintosh files Does not support NetWare file and directory Supports NetWare file and directory permissions during NetWare migration permission during migration Does not support NT file compression Support NT file compression Can be converted to NTFS at any time Maximum partition size of 4GB NTFS can never be converted to FAT. The only way to go from NTFS to FAT is to backup the data, reformat the partition as FAT, and then restore the data to the new FAT partition. Maximum partition size of 16EB

20 How does the file system handle security? Main method of protection is through access control Accessing file system operations (ex. modifying or deleting a file) are controlled through access control lists or capabilities Capabilities are more secure so they tend to be used by operating systems on file systems like NTFS or ext3. 20

21 NTFS Permissions 21 C NTFS Volume Suggestions Available Only on NTFS Volumes Secure Folders and Files Effective When a User Accesses the Resource: Locally Remotely R R R User1 User2 User3 Server User1

22 NTFS Managing NTFS Permissions The only file system supported by Windows XP that offers file-level security File and folder permissions are nearly identical NTFS file and folder permissions Read Write (folders) Write (files) 22

23 Managing NTFS Permissions (continued) 23 List Folder Contents (folders only) Read & Execute (folders) Read & Execute (files) Modify (folders) Modify (files) Full Control (folders) Full Control (files) Special Permissions

24 Standard Permissions Are a Combination of Individual NTFS Permissions Give You the Ability to Assign Multiple NTFS Permissions at One Time 24 Folder Permissions No Access (None) Read (RX) Change (RWXD) Full Control (All) File Permissions No Access (None) (None) Read (RX) (RX) Change (RWXD) (RWXD) Add (WX) (Not Specified) Add & Read (RWX) (RX) List (RX) (Not Specified) Full Control (All) (All)

25 Ownership By default, owner is entity that created the object 25 Owner can change permissions, even when denied access to the object By default, Administrators group is given Take Owner of files and other objects

26 Write Standard NTFS permissions In folders allows new files and folders to be created Folder attributes can be changed Ownership can be viewed For files allows data to be written, attributes changed, ownership viewed 26

27 Read Standard NTFS permissions For files and folders allows files and folder data, attributes, ownership and security to be viewed List folder contents Folders only- allows contents to be listed 27

28 Read and execute Standard NTFS permissions For folders - allows read access to files and folders below For files read access and, if application, ability to run Modify For files and folders - same as write and read/execute plus allows deletion 28

29 Full Control Standard NTFS permissions 29 For files and folders same as modify plus change permissions and take ownership Special permissions more granular options

30 Special NTFS Permissions 30 Permission to Change Permissions & Take Ownership Owner, Administrator ~~~~~ ~~~~~ ~~~~~ ~~~~~ Change Permissions Take Ownership Standard Permission Read Special Access Permissions Read Data Read Attributes Read Permissions Read Extended Attributes Users, Groups

31 علی نیک فرجام ) 31

32 Special Permissions inheritance Inheritance settings This folder only This folder, subfolders, and files (default) This folder and subfolders This folder and files Subfolders and files only Subfolders only Files only علی نیک فرجام ) 32

33 Managing NTFS Permissions (continued) 33

34 Managing NTFS Permissions (continued) 34

35 Managing NTFS Permissions (continued) 35

36 Converting File Systems For highest security, partitions and volumes should be configured to use NTFS FAT and FAT32 volumes on a system Can be migrated to the NTFS format without losing data To convert an NTFS volume to FAT or FAT32, you must: Back up your data Reformat the volume Restore your data 36

37 FAT -> NTFS Convert Command-line utility, CONVERT, will convert FAT or FAT32 partitions and volumes to NTFS All existing files and folders are retained CONVERT cannot convert NTFS to FAT or FAT32 CONVERT drive: /FS:NTFS Requires some additional disk space for NTFS 37