My Macs use Time Machine for backups. The external disk I use to back up my MacBook Air was full up. What Time Machine does when this happens is to delete the oldest backups to make room for new ones. It does this automatically and is alright as far as it goes. The thing is, I didn’t want to loose my older backups just yet so I needed a bigger disk. As it happens, the disk I was using was actually a partition of a bigger disk, so all I had to do was re-partition the disk from two to one. Simples!
Well no, actually. Partitioning destroys the data on the disk, so I needed to copy the existing backup elsewhere first, repartition the disk and copy it back. Luckily I had another external disk with a free partition that was just big enough to take the existing backup. Apple says you can just copy the Backups.backupdb file using Finder. Opinion is divided on this, Apple says you can. I says you can’t.
I tried. The copy took many hours (which I expected) but stopped dead with about 10GB to go. I left it overnight, just in case it decided to finish in its own good time, but the following morning it was still the same. So I dug out Carbon Copy Cloner (my weapon of choice for cloning tasks) to do a block-by-block copy of the old disk to the temporary one. Better! Now I’m not one to take things like this on trust so I pointed Time Machine at the temporary disk and restored a really old file. Tick.
That left me free to re-partition the “real” backup disk and copy the backup back (huh?) Just for the hell of it, this time I tried Apple’s method on the newly partitioned disk. It worked but it didn’t. Back in Time Machine I could see files in the backup library but they would’t restore. That wasn’t much use! So, back to CCC and a block-copy back again. This time when I pointed Time Machine at the volume I was able to test restore several files from random points in the past. So I have a working backup which I can restore from, with plenty of capacity for future Time Machine backups. Incidentally, none of the foregoing was difficult, it just took a bit of time.