Time Machine stuck at "preparing backup"

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Level 1

19 points

Time Machine stuck at "preparing backup"

A few days ago I noticed that Time Machine had stopped backing up. I discovered that my external disc drive was no longer showing as connected to my iMac. I did a quick reboot by physically disconnecting the external hard drive — a WD Passport for Mac — then reconnecting to the USB port, which seemed to fix the problem. Except that since then every morning when I reboot from a cold start I have to reconnect the external disc. Time Machine has begun sticking at the "preparing backup" stage and is not backing up. I'm wondering what's going on and if the problem is with Time Machine or with the external disc. I've run a diagnostic on the external disc with both Disc Utilities and the WD Drive Utilities application, but nothing bad is showing. Any thoughts? I'm still using the Catalina operating system version 10.15.7.

iMac 21.5″, macOS 10.15

Posted on Mar 18, 2022 4:00 PM

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Answer 1

Best reply

Keith Barkley

Level 6

19,772 points

Mar 18, 2022 7:46 PM in response to jayceevee

When it has to scan the whole disk it can take *days* to "prepare backup" be patient and give it time, or erase the drive and start fresh.

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Answer 2

jayceevee Author

Level 1

19 points

Mar 22, 2022 2:53 PM in response to Keith Barkley

Your advice was spot on. I now know that Time Machine is not a fault. It works just fine once the external disc drive has been recognized. Now I need to determine why my iMac suddenly began failing to recognize my external disc when I boot up in the morning. If I physically disconnect the USB cable for a few seconds, then plug it back in the external drive shows up and everything is fine until I shut down for the night. I have even ejected the drive before shutting down the iMac, but the non-recognition problem persists.

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Time Machine stuck at "preparing backup"

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