If data is overwritten in flash can it be recovered

^ Is for files that have deleted But NOT over written.
To recover files that have truely been overwritten, it is a rather expensive procedure.

A little explanasion (using magnetic, but princile for flash is simular). The media contains sectors (512 bytes) and is grouped in clusters, normally 4 K (8 sectors). If you write a file that is smaller than 4 K . When you format the drive a file allocation table is created listing the clusters (all marked as unused.) When you write a file less than 4 K it uses 4K. If you write a file that is say 21 K, it would use 6 clusters, at the end of a cluster is a pointer that points to the next cluster (repeated until a EOF (EndofFile). When you delete a file it marks the clusters as available BUT the DATA is still there along with all the pointers and can be recovered rather easily.
UNTILL a new file write is requested and if that request uses the "availble cluster" that was used then the data is overwritten and the cluster pointers are now for the new file. If new file only over wrote say 8 K of the "Deleted" file the remaining clusters still have the old data, But since 8 K have been over written it may look like pure gaurbage.
If you reformate a drive the data is all still there, but since formating will rewrite the file allocation table, You can read each cluster and recover each cluster - You have to put the clusters togeter. - easy if file wrote to seceeding cluster, NOT so easy if file was fragmented. Note there may be a back-up file allocation table that you can revert too.

If the file is really over written, then recovery becomes expensive. Equipment has to be employed that can look at a "Domain" that has changed and be able to detect what it Use to be. As the number of "writes" to a sector increase, the more difficault the recovery, after about 5 overwrites almose impossible to recover.
 

COLGeek

Cybernaut
Moderator

Chief,

Excellent tutorial, my friend. You did good.

COLGeek
 

technops1

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Apr 15, 2010
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Oops, you need a deep scan on your flash. How? I used some program and it offers deep scan, namely RAW scan. It scans every possible data on your flash which might date data back to many years ago.

No kidding, i am thankful for guide http://www.geeksdo.com/data-recovery/ since it saved big for me when i lost my files on my sd card - fabulous photos i took. I did not post to let you purchase their program. You can use free trial.

Once data is overwritten, many people would say they cannot restore such data. However you can use software to try since it does not require you to pay for scanning.