[Leica] really elementary backup question

[kcarney1 at cox.net (Ken Carney)]

I see from Martin Evening's book that the LR catalog should be backed up 
manually.  I assume this is because it is checking for errors.  For 
other backups, I use SyncBack.   It backs up my internal drive with my 
photos to two external drives each week, at 2 a.m.  Then about once a 
month I back up that internal drive to a third external drive.  When the 
automated backup occurs, how would I know that some internal drive files 
have not become corrupted, and I am just backing up worthless data?  I 
realize this is a really basic question, but my choices are to ask the 
our consultants at the firm and probably get deer in the headlights, or 
get an understandable answer from the LUG.  Thanks!

Ken