Time Machine backup to drive on another Mac?

[Mistercharlie]

I want to back up an old 2012-ish MacBook Air over the network to a drive connected to my M1 Mac mini.

I also want to create a local backup to a 128GB SD card in the MacBook.

The mini is connected via Ethernet, the MacBook is Wi-Fi-only.

Finally, one of these backups will be Time Machine, the other will with Carbon Copy Cloner.

Suggestions on how best to set it up, please! for instance, should the CCC backup go to the SD card, or the SSD drive connected to the Mac Mini?

 

[chabig]

Personally I would set up Time Machine to go to the Mini, and use CCC to make a bootable clone on the SSD card. Set up Time Machine on the Mini like this:

Mac shared as a Time Machine backup destination

 

[Mistercharlie]

I was thinking of putting Time Machine on the SD card to reduce network traffic, but I also figured Time Machine would be more robust if the source Mac sleeps while backing up.

(The source MacBook belongs to another family member who never remembers to back up manually)

 

[chabig]

My setup is similar to yours. I've set my Mini to be a Time Machine server by following the linked instructions. As you know, the M1 is very power efficient, so I've also set it to never sleep.

If the owner of the MacBook never remembers to backup manually, they will never notice the SD card in the memory card slot. You could forego a clone and just use Time Machine on the SD card as well (TM can backup to more than one destination). This way you'll have a Time Machine backup on the machine itself, and a networked Time Machine backup that updates when the machine is connected to your home network.

 

[Brian33]

I think there is value in using two different backup systems. If backups stop working due to a software bug and the failure is not noticed, the second system will (probably) not have that same bug and will have been working normally.

I use (and like) both Time Machine and Carbon Copy Cloner. So I think your original plan is a good one -- and it's given me the idea of using a local SD card for my household's portable Mac. (Currently it's backed up by TM to our Mac Mini, and I do monthly CCC backups to an external drive.)

but I also figured Time Machine would be more robust if the source Mac sleeps while backing up.

Regarding sleep: I know for my iMac, CCC will prevent sleep until the backup is done. With the portable it might possibly be different (there's a lid to close), but I think CCC will prevent sleep until it's done. Only a test will tell for sure.

As far as which backup to be remote and which local, I think it's about a toss-up. Both systems have the capability of remote backups. I think I'd go with TM for the remote, though. (1) it seems to me that that's one of its main design criteria, and (2) I think it'd have less network traffic than CCC! For a normal backup, TM doesn't need to scan the timestamps of all the files in the last backup -- CCC does, to determine which files need backing up by comparing timestamps. TM can (usually) use journal info kept by HFS+. (By my understanding.) On the other hand, network usage may not be a significant issue.

I'm wondering about SD cards for backup purposes, though. Don't they have a significantly lower reliability compared to HHDs?

 

[Mistercharlie]

I think I'd go with TM for the remote, though. (1) it seems to me that that's one of its main design criteria, and (2) I think it'd have less network traffic than CCC! For a normal backup, TM doesn't need to scan the timestamps of all the files in the last backup -- CCC does, to determine which files need backing up by comparing timestamps. TM can (usually) use journal info kept by HFS+. (By my understanding.) On the other hand, network usage may not be a significant issue.

Good point. I was thinking more of how Time Machine runs hourly, but this is probably more pertinent.

I'm wondering about SD cards for backup purposes, though. Don't they have a significantly lower reliability compared to HHDs?

I think so, but an SD card is much more reliable than no backup!

 

[Mistercharlie]

Update for anyone who’s thinking of doing the same.

I ended up using Time Machine for both the networked SSD and the SD card, although I may change one in future.

So far it seems to be working fine.

The Time Machine control panel let me format the SD card when I added it as a destination.

For the network backup, I mounted the SSD connected to my Mac mini from the Air, via the Finder. Then I just chose it as a backup destination. Really easy. 👍.