1. Optimizing Disks
CGS2564

2. Disk Directory
What files are on the disk

3. File Allocation Table
Where files are located

4. File Allocation Table
Files deleted and reduced in size

5. Disk Directory
File increases in size

6. File Allocation Table
File increases in size

7. File Allocation Table
File increases in size
Chain of Clusters

8. Fragmentation A normal occurrence Over time - slow disk access
Defragmentation
Puts all files in contiguous clusters

9. Check Disk Fixes physical and logical disk problems Physical Logical
Checks for bad sectors
Moves data to good sectors if possible
Updates FAT (don’t use this sector)
Logical
Corrupted FAT
Lost clusters
Cross linked files

10. Corrupted FAT
Repairs table from second copy if possible

11. Lost Clusters
FAT shows clusters in use but no entry in directory for them or
Directory lists file but no (or incomplete) entries in FAT
Lost Clusters

12. Lost Clusters Causes Symptoms
Power failure (especially during disk access)
Not closing files and exiting programs properly
Not shutting down Windows properly
Symptoms
Can’t open file
Frequent system lockups
Especially during disk access
Other “strange” problems

13. Lost Clusters Check Disk What to do with them?
Converts lost clusters to files
What to do with them?
Examine in editor
Determine if they contain recoverable data
Open in application and salvage what you can
Otherwise delete
Run applications and reinstall if necessary

14. Check Disk
Disk with corrupted file

15. Check Disk
Recovered files stored in FOUND folder

16. Check Disk
Recovered file examined for clues to its content