Please explain Unmovable clusters & bad sectors

[winterlude]

When I defragment my harddrive, I see fairly large areas of the disk that represent data that will not be moved. My assumption is that the more data that can't be moved on my disk, the worse the performance will get.

What causes these unmovable clusters? Is there a critical mass of unmovable clusters that when reached will make the drive impossible to defragment? Or are these unmovable clusters permanently defragmented and actually as fast or faster than other parts of the harddrive?

What causes bad sectors?

Thanks in advance

 

[Mark R]

Unmovable clusters contain critical system data - such as the boot files, the page file, and important system files. They are unmoveable because they are either in constant use by the system (e.g. the registry) or moving them will cause the system to malfunction (e.g. boot files).

The files that they contain are not necessarily defragmented, and are not stored on any particular part of the hard drive.

Even after defragmentation, a file may still be fragmented where it crosses an umoveable file - however, this low level of fragmentation is unlikely to be significant.

 

[LordOfAll]

Really large blocks are probably the swap file. If you have a desent amount of ram (128MB) you can turn the swap file off temporaraly to defrag. Bad sectors are sectors that scan disk or similar software has done a surface scan on and found to be unreliable. They are marked out and not used again.