Shifting Time Machine backup to new External

I use an external dock - I can swap out internal drives on it. When the first one got full, I simply ejected it and put a blank HD in it. Time Machine then did a FULL backup, as though it were a new (first time) backup, and now it does incremental backups normally.

My plan is to rotate between these two drives - when Disk #2 gets full, I'll rotate back to Disk #1, etc.

You'll have to designate the new drive as your Time Machine drive, but that's a simple task. TM will take it from there.

 

Well, if I may play Devil's Advocate, why would you want to?

Think of it this way - you bought a bigger drive for more Time Machine capacity. You could theoretically do this in one of two ways:

1. Move everything from the old (smaller) drive to the new drive, taking up quite a bit of its capacity, then perform incremental backups from that point. Keep the old drive for...whatever sounds good to you.

2. Leave everything on the old (smaller) drive, giving you even more space on your new, larger drive. Keep the old drive, just in case you want to roll back even farther than the data on your new drive.

Either way, you'll have a complete backup on your new drive, you'll have all your old data, but with option 2 you'll have even more blank drive space available.

But to answer your question more directly - I imagine you could use some sort of disk clone utility to copy everything over to the new drive, I can't vouch for one because I've never used one. But I suppose it's possible.

 

Make sure both drives are connected & then launch Disk Utility. Click on one of the drive names in the left column (the main drive icon, not a sub-icon) & click the Restore tab across the top (far right). Then drag the icon of the older/smaller drive to the Source field & the icon of the new drive to the Destination field & click Restore. I found it worked best with Erase Destination checked, which is not a problem with a brand-new drive. When this is done copying & verifying (at least 2-3 hours!), the new drive will have the same name as the old drive.

 

Super duper will clone it.