I bought a new 5TB HD yesterday to use as a back up drive, replacing the 3TB one I have as it is full.
I followed the official instructions on the Apple site and am now migrating the files from one to the other. However, so far, nearly 24 hours have elapsed and it is just about half done.
I am now wondering if I should have just set the new HD to back up the old one using Time Machine. The way I am doing it is supposed to preserve everything and it will, when I select it, function exactly as the old one, but with another 2 TBs free. But I am wondering if using Time Machine would have had the same effect?
At least, backing up with Time Machine, I can stop and start the process, whereas I am now stuck with running my computer for another 24 hrs.
I know I could have retired the old HD and hook it up if needed, starting afresh with the new one.....but I wanted the old drive for other purposes; so didn't go down that route.
Sounds about right (My last 1.6TB backup took ~27 Hours using USB 2.0).
One thing that'll likely be slowing it down is the fact you have two hard drives connecting through the same USB controller. This effectively halves the data throughput and if it's USB2.0 then it'll be really slow. You can buy special controller cards which have a dedicated controller for each port but they're somewhat expensive (~£120-150).
Also depending on the software/settings used, it may be performing CRC checks/write verification which can slow it to less than half speed again. Personally I'd never transfer data between backup drives without this, too much at stake just for the sake of a few more hours.
Seriously though, are you saying you're only going to have a single backup drive?
The computer is an iMac so can't add cards etc. My backup is so large as it not only backs up the internal HD, but other external HDs as well. I am toying with the idea of getting a second 5TB drive to back up 'the back up'......which has partly prompted my query as I don't want to sit through this again (still 9 hours to go!!). I feel quite secure however, as when this finishes I will have two copies of everything....so no rush to add another backup.