Time Machine dialog: Which 'disk' to choose if you just want to do a one-time full backup to a new external drive?

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Level 1

16 points

Time Machine dialog: Which 'disk' to choose if you just want to do a one-time full backup to a new external drive?

I want to do a full backup to an unused hard drive that's pre-formatted for Windows.

I saw an article that suggested I could just go directly to Time Machine without using Disk Utility, and that the required reformatting would occur in Time Machine.

However, the 'select disk' option in Time Machine displayed only options to "Replace" my current default backup disk or to use "Both".

At the moment I just want to do a one-time full backup to the new drive. If I select "Replace" will that have any affect on my normal partial backups that go on the default backup disk?

(The use of the word "Replace" is strange -- i.e., if clicking that button doesn't actually "replace" the default drive for future backups, why not just label the button "Use new media for this backup" or something similar?)

Mac OS Mojave (10.14.3)

2012 MacBook Pro

Posted on Apr 29, 2024 6:17 AM

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Answer 1

muguy

Level 9

76,591 points

Apr 29, 2024 7:32 AM in response to ddow77

If you replace, your old drive will no longer perform incremental backups as it will no longer be recognized as your Time Machine drive.

I'd select Use both. That's effectively what you'll be doing. The new drive will have a current full backup made on it. The old Time Machine drive will continue incremental backups From where they left off.

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Answer 2

ddow77 Author

Level 1

16 points

Apr 29, 2024 6:56 AM in response to muguy

Thanks but I don't understand the use of the word "replace" here.

I just want to do a one-time backup to the new disk -- to get a single new full backup -- and then go back to doing the standard partial backups on the original backup disk. I don't want to "replace" the current backup disk.

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Answer 3

ddow77 Author

Level 1

16 points

Apr 29, 2024 7:21 AM in response to muguy

The in-dialog-box info re: "Use both" says that if it's selected TM will then alternate backups between the two backup disks.

That's not what I intended.

If I choose "Replace" will that have any effect on future TM backups to the original backup disk?

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Answer 4

ddow77 Author

Level 1

16 points

Apr 29, 2024 7:30 PM in response to muguy

OK, I guess "Replace" means that the original backup disk disappears as an option.

In the end, I did select "Both". So now I see both drives and assume I can choose between them when backing up.

The on-screen wording seemed to me to indicate (and still does) an automatic alternation between them:

"If you use both, Time Machine will take turns backing up to [original drive] and [new drive]."

Thanks for your replies.

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Answer 5

muguy

Level 9

76,591 points

Apr 29, 2024 6:52 AM in response to ddow77

Replace will replace whatever drive you currently use for Time Machine with the new one.

Use both allows you to swap the hard drives to perform incremental backups on each should one fail.

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Answer 6

muguy

Level 9

76,591 points

Apr 29, 2024 7:03 AM in response to ddow77

Then you’ll need to select use both.

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