Time Machine Says I need 4Tb to Backup 1Tb

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22 points

Time Machine Says I need 4Tb to Backup 1Tb

Time machine didn't delete old backups when disk became full like it was supposed to. So I had to erase the external 2Tb drive, after deleting all the files manually I use, to backup my 1Tb HDD in my 2013 iMac. I then reformated it with journal as usual and ended up with a clean 2tb Apple ready drive.

All is OK according to disk utility. I've unmounted/remounted, unplugged iMac and powered up from scratch but when I try and do a Time Machine backup it says I need 4.2 Tb. I only have that 1Tb HDD in my iMac. I have a few external USB drives but they don't appear on the list to not backup and they were never backed up before. Also they total more than 4.2 Tb.

So what is causing Time Machine to ask for 4.2TB ? I assume this would be the first full backup it does and then incremental. I use Time Machine now and then to recover lost files and apps so its important. But this is frustrating. Any help appreciated

iMac Line (2012 and Later)

Posted on Dec 15, 2019 6:27 AM

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Answer 1

1topgazza Author

Level 1

22 points

Dec 15, 2019 6:55 AM in response to 1topgazza

Update: If I unplug my USB drives the amount required drops. Time MAchine has never backed up the external drives before so why is it now deciding it will ? This is appalling as I cant deselect the drives. Sometimes Apple takes away too much control and this appears to be a prime example.

So how do I get Time Machine to just back up my iMac HDD and nothing else ? It seems to include the external Time Machine backup drive as well. Again, it has never included anything other than my HDD before

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