I have a MacBook Air 2023 running Sequoia 15.3.2. Time Machine won't back up to an external Sandisk Extreme formatted to MacOS Extended (journaled). I would appreciate help and suggestions.
MacBook Air 15″, macOS 15.3
In Disk Utility go to the small View box and select Show All Devices.
Select the first icon listed for the external drive.
Erase and format it GUID Partition Map / APFS.
see > Initialize an external storage device in Disk Utility on Mac - Apple Support
and then > Back up your Mac with Time Machine - Apple Support
Is this a new Sandisk Extreme or one that has other data stored on it...?
You should not use the same external drive for storage and backup.
If the Sandisk is new and empty...
Then reformat it GUID Partition Map / APFS.
If the Sandisk has other data stored on it...
Then get and use a second external SSD or HDD for Time Machine backups.
I did have other files on the SanDisk, so I erased it and reformatted it to MacOS Extended (APFS?).
The external SanDisk shows up in Finder, but when I try to back up to it, I get an error message, "Try backing up again when "SANDISK EXTREME" is available".
I've ejected the disk, rebooted and re-plugged in the SanDisk. It shows up in Finder but TimeMachine still won't back up to the SanDisk.
I ran Disk Utility on the SanDisk (again), and got this error message:
Running First Aid on “SANDISK EXTREME” (disk4s1)
Checking file system and repairing if necessary and if possible.
Volume could not be unmounted.
Restoring the original state found as mounted.
Unable to unmount volume for repair. : (-69673)
Any insights to this problem?
Time Machine backup to Sandisk Extreme
