1. The disk surface is divided into tracks. into tracks. 1

2. Track 0 Track 1 Track 79 2

3. Side 1, Track 0 Side 1, Track 0 Side 2, Track 0 Side 2, Track 0 3

4. Most hard drives have multiple platters. 4 Platter1, Track1 Platter2, Track1 Platter3, Track1 Platter4, Track1

5. The eight track 1’s are referred to collectively as “Cylinder 1.” 5

6. Read\Write Head Read\Write Head Platter 6

7. 7

8. 8

9. One Sector = 512 Bytes 9

10. Cluster 10

11. 11 ClusterCluster  The smallest unit of disk space that the operating system can allocate to a file.  It consists of one or more sectors.  Generally, the larger the disk drive; the more sectors per cluster.

12. 12 File Allocation Table (FAT)  OS’s road map to the disk  How the OS keeps track of which clusters belong to which files  How the OS keeps track of bad sectors  Two copies maintained and kept up to date.

13. 13 FormattingFormatting  Low Level Formatting - Performed by the Drive Manufacturer.  High Level Formatting - Performed by the PC User via the FORMAT Command.

14. Blank Disk Sectors and tracks defined Low-Level Formatting

15. 15 Low Level Formatting  Performed at the factory.  Converts the single blank surface into tracks and sectors.  Finds and remaps bad spots on the disk so that the operating system can avoid them.

16. 16 High Level Formatting  Originally performed by the vendor of the computer.  Creates boot record, FAT, and the root directory.  Performed with the FORMAT command.

17. 17 PartitioningPartitioning  Makes the hard disk compatible with the OS  Prepares hard disk for high-level format  Divides hard disk into partitions or makes it one large partition  Performed with the FDISK utility

18. 18 FAT and FAT 16  DOS, Win 95, Win 98  2 GB Maximum Partition  32 KB Cluster @ 2 GB

19. 19 VFATVFAT  Win 95 and Win 98  2 GB Maximum Partition  32 K Cluster @ 2 GB  Long File Names

20. 20 FAT 32  Win 95, Win 98, Win ME  2 TB Maximum Partition  4 KB Cluster @ 2 GB

21. 21 The File Allocation Table contains a 16-bit entry for every cluster on the disk. For this reason, the system is called FAT16.

22. 22 However, 16-bits can represent only 65,536 clusters.

23. 23 The FAT16 system used by MS- DOS and Windows 3.X is limited to 65,536 clusters.

24. 24 Because of this limitation, cluster size increases as disk size increases.

25. 25 FAT 16 Disk Size vs. Cluster Size 16 - 127 MB 128 - 255 MB 256 - 511 MB 512 - 1023 MB 1024 - 2047 MB 2048 bytes 4096 bytes 8192 bytes 16,384 bytes 32,768 bytes

26. 26 No matter how small the file, FAT allocates the entire cluster.

27. 27 A short text file might require only 1000 bytes. But on a 2 GB drive, the cluster size is 32,768 bytes. In this example, 31,768 bytes are wasted.

28. 28 The wasted bytes are called “cluster overhang.” Cluster overhang causes a lot of wasted space. The larger the hard drive, the greater the wasted space.

29. 29 Windows 98 has a way of overcoming this problem. Windows 98 uses a system called Virtual File Allocation Table or VFAT.

30. 30 In order to maintain backwards compatibility with earlier files, Windows 98 accommodates FAT16 files.

31. 31 At the same time, Windows 98 has updated the FAT system to a new FAT32 system.

32. 32 Advantages of FAT32  Smaller cluster sizes  Support for larger hard disks  Improved reliability  Flexible partitioning

33. 33 FAT32 Disk Size vs. Cluster Size 16 MB - 8 GB 8 - 16 GB 16 - 32 GB Over 32 GB 4096 bytes 8192 bytes 16,384 bytes 32,768 bytes

34. 34 Windows 98 comes with a utility called Drive Converter (FAT32) that converts FAT16 partitions into FAT32 Partitions.