Monday, October 31, 2011

Overwritten memory chip

Data recovery is all about get data back when it has been lost.  Often this is possible but there is one case when it just cannot be achieved.  The problem is when the physical area,sector has been overwritten.

Whe a file is deleted, normally the index, or directory entry is removed. When a disk is formatted, generally only the key areas on the disk are written to.  In both of these cases, old data will exist, and programs such as CnW Recovery will  find the data.

When a sector is overwritten, the data is lost.  If there are no backups of the data, there is nothing that can be done.  There are suggestions that with a hard drive, unless data is overwritten 7 times, then it could be recovered - the author is extremely sceptical of this due to the exceptionally high density of current disks.  What may have been possible 20 years ago, is no longer the case.  For memory chips, it is also very definate.  There is no scope of reading slightly off track and getting data back.  It could be argued that routines that process wear leveling could point to old data, but this would only be a maximum of about 5% of the data, from any period of the disk.  It will not contain a complete photo.

With cameras, because there is no editing, there is no requirement for any backups.  The conclusion is that an overwritten photo is lost.  Take care.