1. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Chap-3
Unit-1

2. LINUX SUPPORTED FILES: VFS
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
LINUX SUPPORTED FILES: VFS
Linux run on almost all platforms therefore is able to support all the file system types that are found on those systems.
Linux can read and write to several different file systems. To facilitate this linux have virtual file system(VFS) layer.
VFS is a kernel software, data abstraction layer that handles all system calls related to file systems.
This layer avoids the duplication of common code between all file systems.

3. LINUX SUPPORTED FILES: VFS
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
LINUX SUPPORTED FILES: VFS
VFS layer acts as a layer between the kernal and the programs that issue file system commands. Its main strength is to provide a common interface to several kinds of file systems.
To see currently files system type we have to type cat/proc/filesystems on prompt.

4. LINUX SUPPORTED FILES: VFS: EXT2
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
LINUX SUPPORTED FILES: VFS: EXT2
EXT2 stands for second extended file system..
It is used as the default powerful file system.
It does not maintain a journal and uses significantly less memory .
It uses the following:
Blocks as the basic unit of storage
Inodes as the mean of keeping track of files.
Block groups to logically split the disk into more manageable sections.
Directories to provide hierarchical organisation of files.
Super blocks to define the parameters of the file system and its overall state.

5. LINUX SUPPORTED FILES: VFS:Ext3
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
LINUX SUPPORTED FILES: VFS:Ext3
Ext3 stands for third extended file system.
Ext3 is a very closely related to ext2 and allows in-place upgrades from ext2 without having to back up and restore data.
It holds features of ext2 with addition.
It supports journaling.
Journaling has a dedicated area in the file systems which track all the changes.
When the system crashes the possibility of file system corruption is less because of journalling.
Ext3 can handle individual file size from 16 GB to 2TB and overall file system size from 2 TB to 32 to TB.

6. LINUX SUPPORTED FILES: VFS:Ext4
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
LINUX SUPPORTED FILES: VFS:Ext4
Ext4 stands for Fourth Extended file system.
It is an extended to Ext3.
It performs better and scales better to large number of files.
It can handle huge individual file size from 16GB to 16TB and overall file system 1EB. ( 1 Exabyte = 1024 petabyte , 1pb = 1024 TB)
Directory can contain a max. Of 64,000 sub directories.
It has many features like
Multiblock allocation
Delayed allocation
Journal check sum
It has a option of turning the journaling feature off.
All this advanced features have improved the performance and reliablity of the file system.

7. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
REISERFS
Reiserfs is a powerful alternative to the Ext2 file system. This is a journalizing file system that used to be the default file system for some linux distribution.
It is designed for fast server performance as it provides better disk space utilization, disk access performance and fast crash recovery.
It pays great care to metadata but not to the data itself.
Future generation of it will include data journalling both metadata and actual data.
It also does not have fixed space allocation for inodes, which saves about 6 percent of disk space.

8. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
JSF
It was developed by IBM to suit the needs of environment where performance is the ultimat goal.
It supports both large files and partitions as it is 64-bit file system.
It dynamically allcates inode space and frees it when it is no longer needed.
It also ensures efficient journaling, directory organization, and better space usage through dynamic inode allocation.

9. XFS: Extended file system
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
XFS: Extended file system
It is a high performance 64-it journaling file system.
It can manipulat large filesand performs wel on high end hardware.
Like reiserfs , XFS concentrate on metadata integrity, but less of data integreity.
It provides high scalability through the use of allocation groups, high performance through efficeint management of disk space and avoids file system fragmetation.

10. NTFS : New technology file system
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
NTFS : New technology file system
It is a b-tree file system, means it has a performance and reliability advantage.
It provides journaling and support for encryption and compression.
The ability to read and write to NTFS is provided by the NTFS-3G driver.

11. FAT : File Allocation Table
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
FAT : File Allocation Table
It is a traditional dos file system.
It was originally created for QDOS and used on 360 K floppy disks.
It handles very large files system.
There are four versions of FAT: FAT12, Fat16, VFAT and FAT32.

12. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Memory & VFS
VFS is developed to provide an abstraction layer between the application program and the file system implementation.
This file systems exist either entierly in system memory or they are virtual.
VFS occupies no disk space and provide information about the running system processes.
Some of the VFSs are as listed ....

13. Memory & VFS : CRAMFS (Compressed RAM FS)
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Memory & VFS : CRAMFS (Compressed RAM FS)
It is a readonly linux file system designed for simplicity and space efficiency .
It has minimum features .
They are designed to CRAM a file system on a small flash memory device.
It is a very simple, compressed and readonly FS, so mainly used in embedded systems and small footprint systems.
File size are limited to less than 16MB and FS is 256MB.

14. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Memory & VFS: TMPFS
It is a FS which keeps all files in virtual memory that is, no files will be created on PC’s hard drive however, swap space is used as backing store in case of low memory situations.
TMPFS lost all the data on system reboot.
The memory used by TMPFS grows and shrinks to accomodate the files it contains and can be swapped out to swap space.

15. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Memory & VFS: RAMFS
They ae basically CRAMFS but there is no backing store in RAMFS.
RAMFS does not use swap and they grow dynamically.

16. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Memory & VFS : ROMFS
It is a space-efficient, small, read only FS designed for boot disks and initial RAMDISKS.
It does not use compressions.
When used with initrd, it can be stored in compressed form on the boot medium and is decompressed in whole while loading it into the RAMDISK.

17. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Memory & VFS: PROCFS
It is used to access kernal information about processes and othersystem information in a hierarchical file-like structure.
The PROCFS provides a method of communication between kernel space and user space. In the /proc FS , VF can be read from or written to as a means of communicating with units in the kernel.

18. Memory & VFS : DEVFS It is used for presenting device files.
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Memory & VFS : DEVFS
It is used for presenting device files.
It provides a tool for checking the avialability of devices.
It keeps tracks of device drivers currently registered and also automatically create and remove the corresponding device nodes in /dev.

19. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Memory & VFS : SYSFS
It holds information about buses, devices ,firm ware, file systems etc.
It exports information about devices and drivers from the kernel device model to user space, and is also used for configuration.
It acts as an interface to the kernel’s internal data structures.

20. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Linux Disk Management
At time of installing Linux the main concern is the partition of disk drives.
Estimation are made regarding the required space for system files and user files.
As storage techniques plays critical role in increasing the performance, availability, and manageability of linux servers.

21. Linux Disk Management: Disk Partitioning
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Linux Disk Management: Disk Partitioning
Various partition schemes supported by LINUX are : UNIXWARE, ALPHA, OSF, SGI, DISKLABLE etc.
Before using hard drive, it must be partitioned and formatted.
FDISK is used for partition and format a drive.
After formatting the harddrive , we have to designate a point which is known as mount point, on the hard drive that the system and user will use to access the hard drive.
To access the new partition, create a directory for it.
After adding the mount point, we need to edit the FSTAB file as per the requirement. This is a file that will be read during boot and wil automatically mount all devices listed,

22. Linux Disk Management: Logical volumes
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Linux Disk Management: Logical volumes
A physical volume is divided into volume groups, which are then combined to form logical volumes.
A volume group is the term used for the logical collections of disks that have been grouped together into one volumes.
Storage volumes created under Logical volume can be resize and move and it does ot need upgrading of FS tools which in turn reduce operational costs.
Volume management creates a layer of abstraction over physical storage and provides much greater flexibility than using physical storage directly.

23. Linux Disk Management: Logical volumes
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Linux Disk Management: Logical volumes
With logical volume management, the whole disk is allocated to a single volume group and logical volumes are created to hold the FSs.
Logical volumes provide flexible capacity, resizable storage pools, online data relocation, convenient device naming and disk striping.
LVM (logical volume management) provides a higher level view of disk storage on a computer system in comparisionto traditional view of disk and partitions.
It provides much more flexibility t system administrator in allocating storage to applications, and logically naming volume groups.

24. Linux Disk Management: Logical volumes
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Linux Disk Management: Logical volumes
In LVM FSs can extended across multiple disks, extend logical volumes without formatting and repartitioning the disk, data can be rearranged on disks, rename logical storage volumes and stripes data across two or more disks.

25. RAID: Redundant Array of Inexpensive Disks
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
RAID: Redundant Array of Inexpensive Disks
It provides data protection solutions for linux storage as it provides a reliable , reduandant means of protecting vital data on a server.
It aims at improving disk performance and provides data redundancy.
Through RAID, information is spread among various physical hard drives using techniques such as disk striping and disk mirroring to achive redundancy, lower latency and/or higher bandwidth for reading and / or writing, and recoverability from hard-disks crashes.
Raid can be deployed using both hardware and software.

26. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Software based RAID
It offers the cheapest possible solution that abstracts multiple devices and provides a single virtual device.
Its performance depends on the server CPU performance and load.
It provides following features:
Threaded rebuild process
Kernal based configuration
Portability of arrays between linux machines without reconstruction
Back grounded array reconstruction using idle system resources, hot –swappable drive support
Automatic cpu detection to take advantage of certain cou optimizations.

27. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Hardware-based RAID
The hardware based array manages the RAID subsystem and presents to the host only a single disk per RAID array.
Most dedicated servers use a hardware RAID controller.
The controller simple presents the RAID as another logical drive.
They do not require processor resources.
It provides a read/write cache, which depend on the I/O workload.
Hardware implementations provide guranteed perforamce, and no computational overhead to the host computer and can support many OS.

28. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
Six Levels of RAID
RAID-0 is not redundant and most efficient arrau type which results in higher data throughput but offers no fault – tolerance.
It requires atleast two disks and uses a method called stripping that writes a data across both drives.

29. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
RAID-1
It provides redundancy, faster performance, no data loss and fault-tolerant environments.
It requires at least two disks and uses a method called mirroring that writes data is written to both drives.
Each drive us exact miror of other drive and can be used if either of the drive fails.

30. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
RAID-2
It uses hamming error correction codes which facilitates drives which do not have built-in errer detection.
Nowadays RAID-2 is not in much use as all the drives supports built-in error detection.

31. Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
RAID-3
It does not allow multiple I/O operations to run simultaneously.
It stripes data at a byte level across several drives.
It requires hardware support for efficient use.
It is used in single user environment.

32. RAID-4 It does not support multiple simultaneous write operations.
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
RAID-4
It does not support multiple simultaneous write operations.
It stripes data at a block level across several drives.
The performance of a level 4 array is very good for reads and provides slow small random writes.

33. RAID-5 It is used in multiuser environment.
Created By : Asst. Prof. Ashish Shah, J.M.Patel College, Goregoan W
RAID-5
It is used in multiuser environment.
It requires at least three and more typically five disks and provides parity among the drives.
This can speed small writs in multiprocessing systems but performance for reads is considerably lower.