Fragmentation defragmentation fragmented computer hard disk drive space allocation files system memory internal external

 
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cluster 1

cluster 2

cluster 3

cluster 4

cluster 5

cluster 6

cluster 7

cluster 8

cluster 9

cluster 10

cluster 11

cluster 12

Now let us suppose that we create four files, File A, B, C and D in this disk. File A takes 1 cluster, file B takes 4, file C takes 2, and file D takes 3. We store them in the free available space, and they start out all contiguous as shown in the next figure:

A

B

B

B

B

C

C

D

D

D

 

 

 

After some time let we delete the file C and by doing this, both the clusters which were occupied by file C, are now free or unallocated. This leaves the disk looking like the following figure:

A

B

B

B

B

 

 

D

D

D

 

 

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Now, we create a new File E that needs 3 clusters. But, as there are no contiguous blocks on the disk left that are 3 clusters long, so we have to split E into two fragments, using part of the space formerly occupied by C. Now our disk is going to look like the figure given next:

 

A

B

B

B

B

E

E

D

D

D

E

 

 

After a slice of time period, let we delete files A and E and create file F which takes up 5 clusters. The disk now looks like the figure given below:

F

B

B

B

B

F

F

D

D

D

F

F

Now we see that the file F ends up being broken into three fragments. This type of data in the disk is called the fragmented data. The example given above is a very simplified example of fragmentation, because the real disks have thousands of files and thousands of clusters, so the problem there is magnified. This gives you the general idea of what happens though.

What a defragmentation program (Like Microsoft’s DEFRAG Program, Norton’s SpeedDisk) does is to rearrange the disk to get the files back into contiguous form. After running the disk defragmentation utility, the Defragmented data on the disk which we were talking about will look like the figure given below:

 

B

B

B

B

F

F

F

F

F

D

D

D

 

The Fragmented and Defragmented data have a lot of importance during the data recovery, in many cases.

Let us consider that we have two crashed disks for data recovery, one has fragmented data and one was defragmented recently. And you have to do data recovery by collecting the data from the surface of both the disks as the FAT and Root information of the files is damaged. In such type of cases the percentage of recovery will be proportional to the defragmentation of the data in the disk.

Obviously, the data recovery from the Defragmented disk will be easy and percentage of data recovery will also be high but on the other hand, the data recovery from the fragmented disk will be difficult and time–taking as well as the percentage of recovered data will also be disappointing.

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