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weskat Author

Level 1

11 points

Copy Time Machine or Start New?

Looking to understand if I should copy the existing TM backup files, or start a fresh new backup on the new disk.

I'm replacing the external drive on my iMac that has been used for TM backups with a new and larger unit.

Would appreciate your thoughts on pros and cons of:

A) starting a fresh TM backup on new drive; holding the old drive for a period to ensure prior files not needed

B) copying over the TM backup files from the old disk drive

My TM backup archive is extremely large -- this is a mid-2010 iMac and the TM backups have consumed 995GB of a 1TB partition.

Full Disclosure: I followed Apples method to copy the old TM backup to new drive, and after 15 hours, Finder was in the "preparation" phase and had not started copying any files. I stopped the copy as this got me thinking if I really needed to retain this much "old archive". In the seven years I've used the Mac, I've never had reason to go back and grab a file from TM backup.

Comments greatly appreciated.

iMac, macOS Sierra (10.12.6)

Posted on Nov 11, 2017 4:20 AM

Best reply

El Deanio

Level 3

804 points

Posted on Nov 11, 2017 7:47 AM

Method A)

I’ve just copied my existing Time Machine Backup to a new drive. It took about 25 hours (over USB 3) but it did the job okay. It took 12 hours or so just to work out what it was about to copy across, then a similar amount of time to copy across about 2.5 million items. The file was similar in size to yours because my backup also goes back to 2010 or thereabouts.

My original iMac had a 750GB internal. My new iMac has 3TB. My Backup HDD is 1TB RAID 1 device. I’ve just transferred to a 16TB configured as 8TB RAID 1 (it has two 8TB physical drives that are now mirrored. I have further partitioned each volume as two 4TB volumes, one of which is now my Time Machine backup.

It seems to be working fine right now although I did get an apparently spurious error message at one point. I think that if you had let it carry on, you will have finished backing up by now. I suggest that you reinitialise or wipe the new drive and start the copying process again.

The reason I got a new iMac is because the other one gave up the ghost. My Time Machine backup saved my bacon. I lost nothing.