Backup to Recover from Corrupted Files


Today’s Question: It seems to me that most backup routines are primarily concerned with drive failure. I lost a lot of my photos because the individual photo files somehow got corrupted. What do you think is the best solution to prevent overwriting good files with files that have become corrupted? As I understand GoodSync, if a file on my data drive becomes corrupted, that corrupted file will be backed up to my backup disk and overwrite the good file. What is the best solution to prevent losing files in the case of file corruption?

Tim’s Quick Answer: This is actually a somewhat tricky issue to solve for, since it can be difficult to know when a file gets corrupted. It is possible that a corrupted file would appear as a changed file, and thus replace the good copy on a backup. A more traditional incremental backup solution would help, though such an approach can be a bit more complicated to restore from.

More Detail: The basic concept of backing up your data is rather straightforward. If anything should happen to a source file, you recover from a backup copy of that file. With a synchronization approach to backing up your photos, however, a corrupted original file may replace the good file on the backup, so that you no longer have a good version of the file to recover from.

With a synchronization backup the backup copy of a file will only be replaced if the original has changed. It is possible that if the source file is corrupted that will be detected as a change and thus the backup will also become corrupted.

Other incremental backup solutions provide a little more flexibility, by virtue of keeping track of incremental changes with each backup. Of course, if a file does become corrupted it is not very easy to recover since you won’t know how far back in your backup history you need to go to find the non-corrupted version of the file.

Fortunately, file corruption is not particularly common except in the case of failing hardware. This is especially true of raw capture photos, since most software will not make changes directly to the source raw files. However, it is always possible for files to become corrupted, and it can be difficult to have a backup solution that protects against this risk.

Performing regular scans to check for a corrupted file structure on your hard drive can help, such as with Disk Utility on Macintosh or System File Checker on Windows.