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Question: External Time Machine Drive – Missing 1.8TB of free space

I have a Western Digital My Book for Mac 3TB external drive which is used as my Time Machine backup.

I've been using this for months however I've had a few messages in the last week saying the free space is low and my oldest TM backup is being deleted. And in the last 24 hours the drive has run out of space completely and the TM backup fails.

I've looked at the drive in Finder and the Backups.backupdb folder is 951GB, there are also two other folders of non-backup data I stored on the drive totalling around 165GB. So in total I can see around 1.16TB of used space.

However Finder and Disk Utility says that there is only 2.6MB of free space available and that 3TB is used. Meaning I'm missing 1.8TB of storage space...

I've tried ejecting and reconnecting the drive. I've run Disk Utility First Aid. I've emptied the Trash. I've rebooted. No change. Also I do NOT have any of the bundled WD software/utilities installed and never have done.

What is causing this and how do I resolve it?

System info:

Mac OS Sierra 10.12.6, iMac (Retina 5K, 27-inch, 2017), Processor: 4.2 GHz Intel Core i7, Memory: 40 GB 2400 MHz DDR4, Graphics: Radeon Pro 580 8192 MB.

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Question marked as Solved

Try re-indexing Spotlight by excluding your hard drive and then remove it. If that doesn't help, you need to erase and reformat the drive.

Spotlight – Re-index

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User profile for user: Matt Temple UK

Question: External Time Machine Drive – Missing 1.8TB of free space