What’s the best way/ software to sync two external drive with scattered image folders on a mac. There may be overlap but for the most part both drives are unique as far as image content but may have overlaps in filenames. I want to make sure I don’t lose any images in the sync process.

Edit: mac software prefered.

  • 5
    This question appears to be off-topic because it is about file management. The content being photos is simply incidental. The same techniques would work regardless of type of file. This probably is a better question for SuperUser.
    – AJ Henderson
    Oct 31 '13 at 19:06
  • So you want to have two external hard drives with identical files/photos on them? Maybe we should address the fact that this is a terrible way to "backup" your data. That would be more on topic then a generic question about how to sync drives that would be on topic at superuser.com and I'm sure is covered dozens of times already.
    – dpollitt
    Oct 31 '13 at 20:40
  • Agreed, this is a super user question. However, to get things going in the right direction, start looking at rsync and (optionally) launchd as possible solutions (and starting points for questions). I just finished writing my scripts for this exact scenario today.
    – tenmiles
    Oct 31 '13 at 21:28
  • care to share the scripts?
    – kacalapy
    Nov 4 '13 at 18:04

If you want both simple and safe, there's one way to go here: get a third drive that's big enough to hold the data on both, copy everything to that, remove the duplicates (using an image deduplication tool), and then reorganize.

You could then choose to put some of the files back on to both of your original drives, perhaps split by date. But either way, if these are important in any way, make sure you've got backups.


The most reliable way is to do a synchronization that will compare file contents when combining. Personally, I use the synchronize functionality of Total Commander for this kind of thing. It is technically shareware, but it will work indefinitely without registering and if you register (which I highly recommend), then you get updates for life. (My Dad got a license when it was a Windows 3.0 program and hasn't paid again since and I got myself a license in college.)


Rsync is a built-in function of the Mac, and it does exactly what you want, but requires command line switches and the use of terminal.

I use a tool called Sykron that uses Rsync on the backend, but offers a fairly friendly UI. It will keep two external drives in sync. Opensource.

  • I use rsync all the time, but I'm not clear on how it will help here. It doesn't really have sophisticated merge tools — it's more about keeping one directories (maybe across a network) like another.
    – mattdm
    Nov 1 '13 at 2:25
  • 1
    I suspect the tool does not offer all the functions of rsync, not sure. however it does offer exactly what the questions asked for 'sychronize between two disks'. It has an option to 'not replace' any file found on one but not the other drive.
    – cmason
    Nov 1 '13 at 12:52
  • thanks i will get that for sure, and apply it using a third drive like mentioned above.
    – kacalapy
    Nov 4 '13 at 18:06

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