1. File and Disk Maintenance

2. File Systems
A file system defines the structure and the rules used to read, write, and maintain information stored on a disk.
Which system used is determined by;
Hardware
Software
Security needs
Need for a dual-booting system

3. FAT???
file allocation table – where the OS records how the disk space is used

4. File Systems
FAT 16 – oldest, created for DOS, supported by most OSs’, cannot be installed on partitions larger than 2 GB, or on hard drives larger than 4GB.
FAT 32 – supports disks from 512 to 2TB, compatible with Windows 98 and up
NTFS – (new technology file system) – better file security (Encrypting File System), disk compression, logging features, reliability and stability. NTFS volumes can not be accessed by DOS, or Windows 95 or Windows 98.

5. File Systems
The operating system keeps track of data (documents, pictures, etc.) by placing it into a file.
To store and retrieve files:
Disk divided into tracks
Tracks are divided into sectors
Sectors grouped into clusters
Number of sectors in a cluster is determined by
Size of the hard drive
File allocation system – FAT, FAT32, NTFS, e

6. When you format a disk the operating systems creates concentric recording bands, called tracks, around the circumference of the disk. Then, the formatting program (in our case Windows XP) subdivides each track into equal parts, called sectors. Although not all of them are shown in the following diagram, there are 80 concentric tracks on a 3 ½ inch high density diskette and each track is divided into 18 sectors. Each sector in turn contains 512 bytes.
So let’s see tracks X 18 sectors X 2 sides X 512 bytes = 1,474,560 bytes = 1.4 MB

7. Tracks
Sectors within a Track
Cluster

8. A hard disk has extremely smooth metal or glass plates called “platters” (vs. the floppy mylar disk of a floppy disk).
Each platter is divided into tracks and sectors by the format operation, like a floppy disk, however the number of tracks and sectors is different. The number of tracks on a hard disk depends on the disk size and the manufacturer.

9. Clusters?
A cluster, also known as an allocation unit, consists of one or more sectors of storage space, and represents the minimum amount of space that an operating system allocates when saving the contents of a file to a disk.
The number of sectors per cluster is dependent on
Type of disk (floppy disk, hard disk)
Version of operating systems
Size of disk
Every sector contains 512 bytes. (NTFS does allow you to change this number.)
The number of clusters per disk is determined by the filing system (FAT 16, FAT 32 or NTFS).

10. DRIVE SIZE Cluster Size
FAT 16
Cluster Size
FAT 32
NTFS
260 to 511 MB
8 KB (16 sectors)
Not Supported
512 bytes (1 sector)
512 to 1023 MB
16 KB (32 sectors)
4 KB (8 sectors)
1KB (2 sectors)
1024 MB to 2 GB
32 KB (64 sectors)
2 KB (4 sectors)
2 to 4 GB
64 KB (128 sectors)
4 to 8 GB
8 to 16 GB
16 to 32 GB
32 KB ( 64 sectors)
>32 GB (up to 2 TB)

11. Example - File size = 2KB
Hard drive = 2GB
FAT 16 – the file will use 1 cluster which is 64 sectors, so
64 X 512 bytes per sector = 32KB – 2KB = 30KB slack space
FAT 32 – the file will use 1 clusters which is 8 sectors, so
8 X 512 bytes per sector = 4KB – 2KB = 2KB slack space
NTFS – the file will use 1 cluster which is 4 sectors, so
4 X 512 bytes per sector = 2KB – 2KB = 0 slack space

12. So, what does this all mean to us, as Windows XP users?
The bigger your disk – the bigger your clusters (because there is a maximum number of clusters per disk).
One way to help alleviate the problem of slack space is to partition the hard drive into smaller “drives”. Reducing the drive size will reduce the cluster size.

13. So what can cause problems with a Disk?
Physical hard drive problems:
Wear and tear on hard disk - Minimize with Power Management and/or Hibernation
Head crash - Minimize by placing system where it will not get knocked around.
Software-related problems:
Viruses -Minimize by using virus protection software
Some error causing conditions to data that may be repairable:
Power surges
Power outages
Locked system

14. Cleaning Up Your Disk
Computer performance depends a great deal on the hard drive.
Need disk space for:
New files
Temporary files
Documents waiting to be printed
Cache files
Cache – storage area for often used information that can be accessed quickly
Recycle

15. Cleaning Up Your Disk Will remove the following;
Disk cleanup is a utility that helps maintain the hard disk.
Intended for hard drives.
Will remove the following;
Internet cache files
Downloaded program files
Offline web pages
Offline lines, & temporary offline files
Temporary files
Files in the recycle bin
Windows components that you no longer use
Installed programs that you no longer use
Catalog files for the Content Indexer

16. Check Disk
The Check Disk utility is a disk analysis and repair utility that examines disks for errors and, where possible, repairs errors.
Checks the logical structure
Checks the physical integrity of the disk’s surface, if it finds a bad sector it will attempt to move the data to another location.
Take care of Lost Clusters

17. What are lost clusters? Lost Clusters: Reasons for Lost Clusters
Have no directory entry in directory table
Do not belong to any file
Take up disk space -
Unavailable for new data
Cannot be retrieved/deleted
Reasons for Lost Clusters
Not exiting program properly
Power surge/failure

18. Lost Clusters Example

19. Check Disk can fix lost clusters
Can fix lost clusters automatically or
Save them to disk as files
Side note:
You can check if you have lost clusters by clicking on a file and comparing the file size in explorer window to status bar files size.

20. Check Disk continued
CAN check/repair local hard drives, floppy disks, and removable drives
CANNOT find/fix errors on CD-ROMs or network drives

21. Check Disk, continued Should be used on a regular basis
The first time you use it you should back up your disk before running check disk.
Close all open programs when using this program, including screen saver
If disk is formatted as NTFS, Windows XP Professional will automatically (without running Check Disk):
Log all file transactions
Replace bad clusters
Store copies of key information for all files on NTFS volume

22. Contiguous and Noncontiguous Files
Windows XP Professional keeps track of data by placing it into a file.
To store and retrieve files:
Disk divided into sectors
Sectors grouped into clusters
Number of sectors in a cluster is determined by
Size of the hard drive
File allocation system – FAT, FAT32, NTFS, etc.

23. Contiguous and Noncontiguous Files
When a file is deleted:
Only entries in FAT deleted
Space file occupied becomes available

24. Contiguous and Noncontiguous Files
Files are:
Contiguous – written to adjacent clusters on a disk
Noncontiguous (fragmented) – written to a disk in nonadjacent clusters.
So a Fragmented Disk has noncontiguous files. It takes longer to read a Fragmented Disk because the head must move around so much going to the various locations of the file clusters.

28. Defragmentation
Rearranges the files on a disk so that all parts of each files are store in consecutive clusters.
It also records the clusters for one file right after the clusters for another file, and in the process, removes free space between files that would result in more fragmentation.
At the end of defragmentation all the unused space is near the inner edge of the disk.

29. Defragmentation, continued
Prior to running Disk Defragmenter:
Run Check Disk and Disk Cleanup
Close All open programs
Allow ample time, can take hours – depends on how fragmented your disk is.
Back up disk