Nothing is more frustrating than to realize that some files of a backup are corrupt and cannot be accessed anymore. This happens of course right at the time when you need the backup or do not have any other version of the file in reach.
One way to prevent this scenario from happening is to use different locations for your backups, for example CDs, external hard drives and USB drives, and to keep multiple copies of them.
Even though you store the backup in different places it is not guaranteed that the files on those devices are not all corrupt, only the chance of it happening is reduced.
One way to check integrity of backups is to use Media Checker, a freeware for the Windows operating system. Media checker works with all files on devices that are currently connected to the computer it is running on. It can scan folders or complete drives to let you know if files can be read or not.
I contacted the author of Media Checker because it was not clear to me how media checker performed the check and decided whether a file was corrupt or not.
The author answered me this way: "Media Checker considers the data to be safe when all the files in all subfolders of a selected media or folder can be read without any error from the beginning to the end. The program list all the files and attempt to read all of them byte by byte until the end."
You can use Media Checker right after you have created a backup to make sure all files are accessible without errors on the storage device, and then regularly to check for file corruption. If files fail the check, you can either start a backup right away again or try recovery options to restore the files on the backup device.
You can alternatively use a program like File Check MD5 which generates checksums of all files you select. Files are not corrupt when the checksum of a future scan matches the checksum of the original scan.
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Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.