Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

What to do with Time Machine backup after migration to new machine?

H

Hat Tric

macrumors member
Original poster
Nov 12, 2018
59
59
Germany
Hi everyone,

I'll be setting up a new mac with migration assistant using a Time Machine backup that's on an external drive (Samsung T5 SSD, MacOS extended file system).

But what to do with the external drive after the new mac is set up? Do I have to erase it and set up a completely new Time Machine backup (preferrably a couple of weeks after migration) or can I continue using this drive on the new machine? The old mac will be retired so no further backups necessary.

Any input would be much appreciated!
 
Hat Tric said:
Any input would be much appreciated!
Click to expand...
Well, OK!

I have read that you can continue to use your existing TM backup on the new Mac, at least in certain circumstances, but I've never tried it. In this case the HFS+ format will be preserved (details below).

Things to think about:

Does your old Mac still work? If it does, the files currently on your Samsung T5 (at least the latest versions) are not critical because they are still on your old Mac. If a month from now you realized some file you really wanted wasn't copied by the migration process, you could recover it from the old Mac. This means a bit less risk if you decide to erase the T5 and start fresh.

What format to use? In recent macOS releases (somewhere between Mojave and Monterey) Time Machine has had big changes. It now uses APFS formatting by default for the backup disk and supports some APFS advanced features (snapshots, clone file and sparse file support). This is supposed to have a bunch of advantages (quicker backups, more reliable backups, space savings). See eclecticlight.co for lots of articles about the changes to TM. (e.g., https://eclecticlight.co/2021/04/12/should-you-back-up-to-apfs-or-hfs/).

Your TM drive is formatted in the older HFS+ format. Reportedly the new TM can continue to use HFS+ backups, but APFS is now the default. In fact, if you erase your Samsung T5 and then tell TM to use it as a backup target, TM will always reformat it as APFS, no matter what format you put it in. The only exception (so I've read) is if it contains an existing TM backup, in which case TM will continue to use the HFS+ format.

Apple seems to feel TM-to-APFS is the way of the future (all new TM drives are set up that way, and macOS now forces the boot drive to be formatted APFS). This may mean any TM bugs in the HFS+ code might be less likey to be fixed. If there is increasing use within macOS of new APFS capabilities like large sparse files and clone files, space on the backup drive could be saved because TM can presrve these features on an APFS drive. Besides, "everybody says" that SSDs should be formatted APFS. (Though I don't think there's any harm if it's HFS+.)

So which way to go, preserve your old file history with the old format, or start fresh with the new?

(I decided to start fresh, but I was able to find put my old backup drive on the shelf for a few months, just in case.)
 
  • Like
Reactions: gilby101 and Hat Tric
Hat Tric, I'm in the same boat as you. I'm waiting for my M2 Mini to arrive and yesterday I got a T7 1TB. (My iMac and TM backup drive are 10 years old). I had to format it to HFS. The first full backup took about 3.5 hours. Once my Mini is up and running well I plan on formatting the T7 to APFS and starting TM all over. I won't do that until I'm sure everything is going well.
 
  • Like
Reactions: Hat Tric
As the others have said here, the key here is the source. If your older Mac that the original TM backup came from is still working, after use use Migration Assistant to restore everything to the new Mac, you could reformat the backup disk and use it for the initial TM backup from the new Mac. However, keep in mind that that initial backup will be the main POTR (point in time recovery) for any new data that gets added to it, meaning that that technically would be the oldest point in time for your backups, and any new versioning would be made pursuant to that time.

But the others are correct; if you let the mac inherit the backup, you'll keep the consistency for the versioning for the POTR.

BL.
 
  • Like
Reactions: Hat Tric
Fishrrman said:
Erase it and start over anew.

(my opinion only, I don't use tm)
Click to expand...

To a degree. The source is still the target for the previous machine. If the OS on original Mac that created the TM backup doesn't have certain functionality (for example, supporting APFS) then by reformatting it as APFS (which it would be by default on the new Mac), you have then permanently lost the backups from the original Mac.

I went from a mid-2011 13" MBA to the M1 Pro MBP via Migration Assistant and the TM backup I have from the MBA. the MBA I have was really flaky on High Sierra, so Sierra was the farthest I went with it, and was rock solid on it. Sierra does not support APFS and because of that, the MBA and the TM backup were formatted as HFS+. That TM backup disk is still a valid target for that MBA, so any reformatting of it for my MBP will permanently delete any backups I have of the MBA.

So it all depends on if the OP is going to continue to use his original Mac for any other purpose. If he is, then not formatting that disk would be the better option.

BL.
 
  • Like
Reactions: Hat Tric
Thank you everyone for the insightful discussion!

The old mac will be retired, maybe I´ll erase it and install Linux. It currently runs El Capitan (macOS 10.11)

I will do the following: migrate data to the new mac. Since I won´t need anything other than the data currently residing on the old mac, I´ll erase the Time Machine backup a couple days after and start a new one with APFS. Keep the old mac as it is for some weeks until I´m absolutely sure that I didn´t forget to transfer something.
 
  • Like
Reactions: Brian33 and MacCheetah3
Hat Tric said:
Thank you everyone for the insightful discussion!

The old mac will be retired, maybe I´ll erase it and install Linux. It currently runs El Capitan (macOS 10.11)

I will do the following: migrate data to the new mac. Since I won´t need anything other than the data currently residing on the old mac, I´ll erase the Time Machine backup a couple days after and start a new one with APFS. Keep the old mac as it is for some weeks until I´m absolutely sure that I didn´t forget to transfer something.
Click to expand...
One extra step you can do if you have the extra storage is a compete image of your older mac using Carbon Cloner or SuperDuper.
 
I just migrated from my MBP (2017) Ventura to my new MB Air Ventura. The migration process was relatively pain-free. It would have been helpful for the migration assistant at the end of the process to have "said" "hey I notice you used Time Machine on your MBP... would you like to use it on your new MBA?" And then help with the process. I figured out that my new MBA can assume the old backups. So all's well. A couple of other not-so-obvious migration challenges... location services and find-my. It would also be useful if the assistant asked what you want to name your new laptop. Not complaining just observing. Love my new MBA M2!
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back