Feature request: compare backup to file system to find corrupted files


Feature request: compare backup to file system to find corrupted files...
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SouthCoast
SouthCoast
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Having been through a chkdsk-induced corruption this evening leading to Windows refusing to boot (I chkdsk'd the wrong drive) I am so glad I had a Macrium Reflect backup from yesterday to restore.

I didn't restore the data, only the small (EFI?) partitions and that was enough to get it working again. Not knowing what else might have corrupted, can I use the Macrium Reflect backup to detect if any files are corrupted post-chkdsk? Obviously those I've edited today will be different, but knowing what's changed would be useful.

Or even to diff between two incremental backups and browse the files that have changed?

On another computer I discovered photos corrupted by data rot, a bad sector, who knows what and unopenable a long while after it happened which was hugely frustrating. A backup strategy with Macrium doesn't help guard against this; AFAIK there is no way on NTFS to detect and prevent.
jphughan
jphughan
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I use a freeware tool called WinMerge to perform these sorts of comparisons. You can compare a "live" system to a mounted image or two mounted images to each other.  But for this sort of comparison, you'd probably want a comparison to compare the full bits of the files by hashing them rather than just checking for differences in size and/or Date Modified timestamps, and that can take QUITE a long time if you want to do it for an entire drive's worth of files.  But WinMerge can do that sort of comparison.  To do this, make sure you choose a "Full Contents" compare, and then when you get the results (be patient), in order to view them more effectively I recommend going to the View menu and enabling Tree Mode.  At that point you'll have a single folder tree to drill into, and differences between each side's versions will be highlighted along the way.  You can also use the View to menu to individually show or hide files that are identical, files that are different, or files that only exist on one side or the other.  And you may not need this capability for this particular purpose, but if your right-click any given file (or folder), you can choose to copy one side's version to the other in order to quickly resolve differences that shouldn't exist.

The trick when comparing Windows partitions though is that many changes will be EXPECTED.  Log files are being updated constantly, and in fact the VSS snapshots that Windows creates for backing up the drive doesn't actually include all of the data on the drive.  (Certain things like System Restore checkpoints and the Windows Search indexing database are omitted.)  So if you're trying to "root out corruption" (no pun intended) on your entire drive by looking for differences, that will be a tall order, because there will be some differences that are appropriate and that should NOT be overwritten by restoring the corresponding files from your backup.  So I'm not sure this mission is entirely practical, to be honest.  For that reason, you might consider limiting your comparison to your personal data folders, where you would presumably know whether any discrepancies found were or were not appropriate.  That will also cut down on your Full Contents compare time.

GO

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