Is there a program out there that will catalogue the contents of each drive, identify the most recent version of each file and facilitate a complete backup of everything in a single location?
I don't know of one that will catalogue the contents of multiple HDDs, compare, and facilitate copying only the most recent version of a file from across multiple drives drives onto a single backup drive. Looks like the others mentioned above are similar to the s/w I use (FreeFileSync), and will compare 2 HDDs, identify the differences, and allow copying of more recent files from drive A to drive B. Not sure of the others, though I assume they do similar, but FFS also gives you the option to:
- Choose how to determine if files are different: by file time and size, or by content (binary comparison)
- Define filters to exclude certain files, file types, or folders
- Prior to sync, view the file comparison results and defined sync actions for each file, and per file change the sync action, if desired (e.g. copy from left to right, right to left, do nothing, etc.)
- Establish custom sync options based on the comparison result, e.g. what action to take if the file: exists in left but not right, exists in right but not left, is newer in left than right, is newer in right than left, has a conflict or cannot be categorized.
Sounds like you're on the right track in consolidating your backups. Whenever I run out of space on my backup HDDs, I get new, larger HDDs precisely so I have don't have to worry about multiple variations or versions of backups spanning multiple HDDs. (Though at one point I did have more than one backup HDDs with various content across each; I found two manageable, but probably wouldn't want to mess around with more, unless I absolutely had to do so...e.g., if I couldn't fit all my data onto a single HDD, in which case I'd probably opt to build a big-ass array as I know some here have done.)
If there isn't a tool that does so automatically, sounds like you'll need to backup 'HDD A' onto 'HDD Backup'. Then backup 'HDD B' onto 'HDD Backup', ensuring that
<a> only files that don't yet exist on 'HDD Backup' are copied from 'B' to 'Backup', and
<b> for files that do exist on 'HDD 'Backup', only copy those that are newer on 'B' than on 'Backup'. And so on for each HDD.
Whatever software you end up using, if you have the backups scheduled and automated, test what happens when the source drive goes offline. At least one backup program I know of (not mentioned here intentionally) assumes the absence of the source drive means it was deleted, and therefore updates the backup to match...by deleting the backup files. (Brilliant, eh?)