Two HDs, how do I copy over only the files that the other is missing?
September 16, 2013 8:27 PM

Two hard drives. HD2 with a bunch of lossless music. HD1 with the same music plus a bunch more music that I've acquired in recent months. I want all of my collection on both drives in case one fails. Besides copying over each new file piecemeal, or deleting everything on drive 2 and just copying the entirety of drive 1, is there a more elegant way to do this? Is there a program or method that will only copy over the files that HD2 doesn't already have?
posted by WhitenoisE to Computers & Internet (11 answers total) 10 users marked this as a favorite
Are they all in the same subdirectories of the same root folder, with the same filename? If so, any of the tons of rsync implementations will do this easily.
posted by mkultra at 8:30 PM on September 16, 2013


Install Teracopy. (x86 or 64-bit available for Windows)

1. Select your music folder on HD2 as your "target folder."
2. Drag + drop the CONTENTS of your music folder on HD1 to Teracopy. (Do not just grab the Music Folder itself, or you will have something like this on HD2: D:/My Music/My Music)
3. Click on "Always Ask" in the upper-right corner and change this to "skip all" (or "overwrite older", if you have newer files with the same name and place in the directory structure).
4. Click "Copy."

I love Teracopy; I use it to make backups all the time.
posted by dhens at 8:44 PM on September 16, 2013


I'm assuming you're on Windows. I use FreeFileSync to periodically sync music and photos across drives. Works well and is free.

(this is assuming that they follow the same folder structure, as mkultra asked)
posted by Gomez_in_the_South at 9:39 PM on September 16, 2013


Seconding Teracopy. It has nice and easy-to-use options for dealing with duplicate files. The only catch is that once you start the copy process, you'll have to wait for it to hit the first dupe before you can give it a command.
posted by Sunburnt at 12:32 AM on September 17, 2013


Yes, I recently ran into this problem with my image libraries. If you're on a Mac, get Chronosync, and don't look back. Trust me.

If the file names are the same and the folder structures are the same on both drives, Chronosync (even upon first use) can detect this and will not re-write the identical files to HD2. As for any new files on HD1 that are not on HD2? It will add them.

If for some reason you want to delete HD2 and just start fresh, Chronosync will sync the drives with one click here too. (Obviously, it will take time.) You can even schedule synchronizations. You can schedule ten synchronizations and put them all in one container that will run when you tell it to.

If you are on a desktop with drives always plugged in, schedule a daily or weekly sync for 3am when you're asleep.

Just make sure your settings are right. Chronosync can be set up so that when you delete a file in HD1, when the synchronization runs it will also delete the file on HD2. Or, you can have it so it doesn't delete the file on HD2; rather it will archive it on HD2. To me, the first option seems more intuitive, the latter seems to be more of a hassle since HD2 will fill up at a faster rate than HD1, creating drive asymmetry and limiting the amount of data that can sync over.
posted by phaedon at 12:37 AM on September 17, 2013


Synctoy does the same in Windows as Chronosync above for Mac. I've used it for years, works great.
posted by defcom1 at 4:20 AM on September 17, 2013


Another, which works under "any operating system with Java support", is MuCommander.
posted by yclipse at 4:55 AM on September 17, 2013


Seconding Synctoy if you're on Windows. Really easy to use. Not as many options as FreeFileSync, but most people don't need the bells and whistles. I'd start there and then move to FreeFileSync if Synctoy isn't doing it for you.
posted by echo target at 8:14 AM on September 17, 2013


Seconding Teracopy. It has nice and easy-to-use options for dealing with duplicate files. The only catch is that once you start the copy process, you'll have to wait for it to hit the first dupe before you can give it a command.

This part is not true: You can choose what you want Teracopy to do regarding duplicates before hitting "Copy" (or "Move") by clicking the part that says "Always Ask" in the upper-right corner.
posted by dhens at 9:36 AM on September 17, 2013


I'm a big fan of Beyond Compare. I've purchased it, but there's a 30-day free trial. It's excellent at file compares, copying and syncing. It installs (on Windows) as an Explorer extension as well, so starting a compare just requires right-clicking on the folder/drive, selecting "Select Left Folder for Compare", then right-clicking on the other folder/drive and selecting "Compare to", then clicking the Synch button.

It's easy to use and has reasonable defaults, but it's simple to change the comparison rules. I use it regularly for to keep archives up-to-date and doing file compares. The only drawback I can see is that it's not flat-out free.
posted by farmerd at 9:56 AM on September 17, 2013


People are assuming you're on Windows. Probably a good assumption, but could you please confirm that? Or do you have these hard drives floating free, and if so, what kind of computer can you plug them into?

There are standard (and free) solutions for Unix (Linux, Mac) systems (rsync and tools built on rsync) and possibly you can get them to work on Windows too.
posted by RedOrGreen at 12:32 PM on September 17, 2013


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