Tuesday, September 3, 2013

Issues about FAT Data Recovery

FAT file system widely used type in the file system of Windows operating system and the FAT32 file format can be read on Windows and Mac , so the possibility of FAT data recovery and the loss data are also becoming popular. Most of the windows recovery software as ac Kvisoft Data Recovery for Mac achieve recovery FAT. But there are some questions Data Recovery FAT file system should be considered if you are to recover data from FAT32 .
Directory fragmentation Problem
If data , there is a problem to be noted that a directory with a plurality of clusters slightly fragmented. ( Associated mainly because of the space will be allocated directly to a file ) because the directory is the second cluster , the cluster directory barely slowed only when needed and room after the first cluster , it is very difficult to completely restore the directory. However, if you are more cluster directory copied in its entirety , or defragment recently , all clusters are related and it is possible to complete the restoration .

File name problem
If the file is deleted , the first byte of the directory OxE5 is changed to indicate that it has been removed . For short file names that should be the first byte of the file name are crushed, and the long file name , you will overwrite the serial number. For data recovery, there may be two problems :
Problem file name completion . If recover deleted files , we need to cover the name of the file name if the file has a long file name , we can find the first signs of long file names. If you delete a folder, the original folder in this directory can be changed or can not be changed .
Duplicate name issue. If a directory is affected canceled its first byte ( the first number in the file name) to be removed ( and replaced 0xE5 ) , there are two files , removes the named as A- and B - 1.txt 1.txt , then their names in the directory as "_ - 1.txt " is changed, this happens when looking to conflicting names.

Solitary directories and solitary files problem
There is also a problem when a directory is deleted after assigned . In this case, the current directory is no longer in the original file or directory so that files and directories are not original directory pointing to them , they can not be found. For example , a list of on the original 210 clusters , then the directory is removed and reassigned to the cluster now stands at 400 , the contents of the cluster 210 still exists, but we can not see to ' directory tree, we can do not know if they are available , these files solitary confinement solitary confinement directory or files called.

Solitary directory

To find lonely the directory , each sector of the data area should be checked , there is no standard for the control required is a way to (not the cluster) to review the first 32 bytes of each sector to see if they are consistent with the structure of the directory. When they reach the directory structure, it should continue the rest of the industry to see more information. Check to avoid for each sector , these directories penchant cluster that is assigned to other files missing. Another similar method is to see the first 32 bytes of each group , whether they can find . " " Directory , because the first directory of each directory has a "." Directory , but this method can not find the first cluster of directory can not find other clips.
During the implementation of the method is a method to solve these problems, the establishment of additional directory address sequence . For example , assume some software and some Unix operating systems assume that all sectors are affected directories , each sector into 16 sections is divided with a size of 32 bytes , assuming that each element is a directory , then from the first point of data area of the first sector numbered starting back , the first element of the list , at number 0, the second to the first directory .
However, there is an obvious problem , each file and directory is a directory on her show , but the root does not have. This is because the location of the root directory (the value of size is also included FAT12/16 ) is stored in the boot sector , not from the directory described in the data area. Some software , this problem by assigning the second root as the number of addresses to be solved in the directory , then starts again assigned to three . This segment of the data area of ​​the first term to the third records.

Solitary File
To lonely to find the file that is currently the best method for a particular file format of the header of the file and the end of the file is based to find . This way is very effective for a file stored in a row, but not recover for fragmented files .
Problem of allocation strategy
Win XP procedure allows the file name to be removed after longer retention time because it is not available with the first allocation strategy . But that does not mean that the use of the first available allocation strategy more data can be recovered , because the contents of the original file space that has been occupied by the groups assigned , then the contents of the file is broken . Therefore , even if it is capable of seeing the file name , but not necessarily, not retrieve the stored data.

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