Sync 2 hard drives without being connected at the same time (Mac)

Question

I've got a 2TB hard drive at home and one at work. I use my laptop to connect to them. I want these 2 hard drives to be exactly the same. But these hard drives will never be connected at the same time. Is this possible?

It means that my laptop needs to track the changes AND copy all new files to its hard drive temporarily. My laptop should act as an intermediate between the 2 external hard drives.

There are lots of syncing options if both drives are connected at the same time, but there seems to be no solution for my specific problem.

Any ideas? FYI: I use a Mac.

Answer 1

There are many solutions to this problem. The 2 easier ones that come to mind...

• Have a 3rd copy of everything on your Mac. More backups never hurt. Run an rsync operation via script whenever plugging in to either environment. This may require the purchase of an additional drive.

• Find a backup solution that suits your needs. It will ideally be able to perform full backups and differentials. You will first need to ensure both drives are identical, the easiest way is to bring your home hard drive into work one day and get them both in sync. Once they are in sync, make a full backup with your software of either one of the drives. You can then perform differentials to get the delta changes since the last full backup, and restore in the other location. Once done working in the other location, perform another differential backup comparing to your last full backup.

The caveat with #2 is that it can get complicated remembering where the last backups were done, and the size of the differentials will always be getting bigger. Once in a while you could perform another full backup to decrease the differential size, but this type of system can get very complicated. You may want to consider making a small folder of "active" work, as I doubt you need the full 2TB or so of data every day, and sync this to your laptop.

Other solutions include synchronization with online file storage services, but this may not be realistic if you have a small bandwidth cap. I'm not aware of any specific software solution that is tailored to your situation, however ifferential backup systems take care of this with ease.

Answer 2

To take a guess at what you're going for here, the best option might be to buy a bus-powered external hard drive that you take with your laptop, treat that drive as the master where you regularly work with your data, and then use Disk Utility or Carbon Copy Cloner to clone that master to each of your backup drives whenever you're at that location.

If you had the two external drives connected to a desktop or other internet-aware host, it would be possible to remotely rsync them--Carbon Copy Cloner mentioned above can automate this, but it would be a fairly advanced process.