Why does "preparing backup" take hours?

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Level 1

114 points

Why does "preparing backup" take hours?

I use a Seagate 1TB drive for backup. I back up about once a month (I know, not often enough!). When I plug in the drive and initiate a Time Machine backup, it takes hours to "prepare backup". I back up about 300 GB. Why does "preparing backup" take so long?

MacBook Air, macOS Sierra (10.12.6)

Posted on Mar 25, 2018 9:03 AM

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Answer 1

Eric Root

Level 10

687,531 points

Mar 25, 2018 9:20 AM in response to Ian Chamandy1

When you wait that long between backups, Time Machine is 'starting over' because it must compare all data in the backup to all the data on your computer. Enough has changed that it can't pick up where it left off.

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