Time Machine drive setup question

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Level 1

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Time Machine drive setup question

What does Time Machine do to set up disk drives?

I just initialized a (previously used) hard disc (not SSD) and created an HFS+ filesystem on it. Time Machine recognized the new drive popping into existence, and offered to set it up as a time machine backup destination. I agreed, and was brought to a brief configuration page. I turned *off* disk encryption, and clicked to set up the disk.

It then brought up a progress bar, 'Preparing "HHH5"' (HHH5 is the name of my volume.) It flashed the progress bar back and forth across the bar extent a few times. Now the progress bar is stuck at roughly 45% of the way across.

I did the same thing earlier and left it sit for about an hour and the bar did not move any further.

Is it possible that it is running an Erase cycle on the drive? The drive is 12 terabytes so erase would take rather long, if that is what it is doing.

If it were for some reason writing complete HFS+ data structures across the drive, I would have expected the progress bar to move over the course of an hour.

MacOS 15.7.2 (Sequoia) -- so 12 terabytes should certainly be supported.

Note that this is *not* the "Preparing backup" step. You do not get to "Preparing backup" until after the drive is initialized. For example at this stage, there is no Time Machine Options button.

iMac 27″, macOS 15.7

Posted on Nov 24, 2025 8:17 PM

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Answer 1

Top-ranking reply

HWTech

Level 9

68,258 points

Nov 25, 2025 9:07 AM in response to sandra-leigh

I thought more recent versions of macOS will only use an APFS volume when creating a new TM backup drive. Sequoia may still be able to utilize an existing TM backup using an HFS+ volume, but i think it may force an APFS volume for a new drive. It may be converting the file system to APFS which may explain the long prep time.

From the following Apple article:

Types of disks you can use with Time Machine on Mac - Apple Support

APFS or APFS Encrypted disks are the preferred format for a Time Machine backup disk. If you select a new backup disk that’s not already formatted as an APFS disk, you get the option to erase and reformat it. If the disk is a Mac OS Extended format disk that contains an existing Time Machine backup, you aren’t asked to erase and reformat the disk.

It is also possible the used Hard Drive is failing or worn out. You can try checking the health of the external Hard Drive by running the third party app DriveDx (free trial period), but it will require installing a special USB driver as well in order to attempt to access a USB drive's health information. Post the complete DriveDx text report here using the "Additional Text" icon which looks like a piece of paper on the forum editing toolbar.

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Answer 2

Owl-53

Level 10

101,983 points

Nov 25, 2025 9:18 AM in response to HWTech

HWTech wrote:

I thought more recent versions of macOS will only use an APFS volume when creating a new TM backup drive. Sequoia may still be able to utilize an existing TM backup using an HFS+ volume, but i think it may force an APFS volume for a new drive. It may be converting the file system to APFS which may explain the long prep time.

From the following Apple article:

Types of disks you can use with Time Machine on Mac - Apple Support

APFS or APFS Encrypted disks are the preferred format for a Time Machine backup disk. If you select a new backup disk that’s not already formatted as an APFS disk, you get the option to erase and reformat it. If the disk is a Mac OS Extended format disk that contains an existing Time Machine backup, you aren’t asked to erase and reformat the disk.

It is also possible the used Hard Drive is failing or worn out. You can try checking the health of the external Hard Drive by running the third party app DriveDx (free trial period), but it will require installing a special USB driver as well in order to attempt to access a USB drive's health information. Post the complete DriveDx text report here using the "Additional Text" icon which looks like a piece of paper on the forum editing toolbar.

I think you could right visa vie Drive format or Drive conversion to APFS / GUID

This would especially true if the drive has already be Formatted HFS ( Journal ) before hand

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Answer 3

Nov 25, 2025 9:27 AM in response to Owl-53

Here's what Apple also has to say:

Time Machine still supports backups on Mac OS Extended format (Journaled), Mac OS Extended (Case-sensitive, Journaled), and Xsan formatted disks.

Types of disks you can use with Time Machine on Mac - Apple Support

So it seems HFS+ is still supported and presumably if offered to erase and reformat and declined, it will leave the drive as HFS+ and use it for backups.

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Answer 4

Owl-53

Level 10

101,983 points

Nov 25, 2025 3:19 AM in response to sandra-leigh

As there are no important data on this drive

Try re-formatting the drive in the newer APFS / GUID Partition Map format

Select your connected storage device and click Set Up Disk. During setup:

Your Mac might ask if you want to erase the storage device so that it can be used for Time Machine. Either erase it or select a different backup disk or volume.

Erase and reformat a storage device in Disk Utility on Mac

File system formats available in Disk Utility on Mac

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