1. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 0 Lesson 8 Secondary Management

2. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 1 LESSON OVERVIEW  Introduction to secondary storage  Evolution of secondary storage  Preparation of disks for use  File systems  Introduction of drives to OS

3. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 2 Three Main Storage Structures  Primary  Secondary  Tertiary

4. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 3 Primary Storage  Registers  Caches  The system’s main memory These are the storage areas that the CPU can access directly.

5. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 4 Secondary Storage_1  Magnetic Disks These are used as extensions of the system memory because they can hold large quantities of data and can retain it permanently, unlike the system memory.

6. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 5 Secondary Storage_2 The secondary storage level is an important aspect of computer design because it allows for programs and data to be permanently stored when the computer is powered down.

7. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 6 Secondary Storage_3 The control and management of secondary storage devices, specifically magnetic disks by the operating system and by the machine itself will be considered.

8. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 7 Tertiary Storage Devices that use removable media  Tape drives  Floppy disks  CD-ROMs These aren’t considered as secondary storage because of their slow speed when compared to magnetic disks.

9. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 8 Preparing Of Disks For Use  Low Level Formatting  Partitioning

10. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 9 Low Level Formatting  Sectors  Tracks  Cylinders

11. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 10 Sectors  Header  Data Area  Trailer

12. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 11 Header The header contains configuration data used to synchronize the read heads with the data, an address field to identify the sector, and a checksum that validates the header.

13. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 12 Data Area The data simply contains the block of data.

14. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 13 Trailer The trailer has checksum or error correction information, used to detect medium defects.

15. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 14 File System  Basic file system  File organization module  Logical file system

16. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 15 Basic File System_1 It is closest component of the file system to the hardware. Its responsibility is to issue commands to the device drivers of the disk, such as retrieving a particular block of data. It doesn’t know about the individual files on the disk.

17. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 16 Basic File System_2 It only has to worry about communicating with the disk controller. It doesn’t change much between different file systems, as it doesn’t deal with the organization of data, which is what really differentiates various file systems.

18. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 17 File Organization Module It does keep track of the files on the disk, as well as where they are located on disk.

19. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 18 Logical File System It provides the interface between the operating system and the real meat of the file system, the previously discussed file organization module. It is where the operating system and user processes can make system calls request file operations, without knowing anything about the layout, location, or anything else about the disk.

20. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 19 Introduction Of Drives To OS  Bootstrap loader  Master Boot Record (MBR)  BIOS  Power On Self Test (POST)  Initial Program Load (IPL) table  Plug eN Play (PnP) Devices  BIOS Aware IPL Devices (BAID)

21. Copyright © Genetic Computer School 2008 Computer Systems Architecture SA 8- 20 General Abstraction Layout in Linux  Kernel  Kernel I/O Subsystem  Drivers for Each Device  Individual Devices