HELP! My SSD is Filling With Invisible Files!

I was worried. My SSD RAID was getting fuller every time I deleted files. This should not happen! It SHOULD get emptier.

While I was using an OWC Thunderblade RAID, this problem could apply to any SSD. The answer, I found in talking with OWC Support, was “snapshots.”

Here’s how to fix it.

THE PROBLEM

Here’s my Thunderblade with a capacity of 7.68 TB, with 504.68 MB in free space.

But, when I total the current size of my files, they only fill 2.9 TB.

Wow! What happened? Where did almost 4 TB of space go????

WHAT CAUSED IT

APFS, the current data filing system for all Macs, is optimized for SSDs. It’s fast, reliable, and designed to protect your irreplaceable data.

To guard your data, APFS creates “snapshots.” These are read-only copies of the parent APFS volume, taken at a particular moment in time. An APFS volume can have zero or more associated APFS snapshots.

In other words, APFS is creating copies of my existing files “just in case” it needs to restore them in the future. Which is great, but these are sucking up all my free space!

NOTE: This is an SSD issue caused by APFS. If your storage uses HDDs, you have probably formatted it as HFS+, which uses a totally different filing system.

HOW TO FIX IT

While these files are hidden in the Finder, they are easy to find and remove using either Disk Utility, provided with your Mac, or Carbon Copy Cloner, a widely popular backup utility.

NOTE: There may be other options, but these are the two I have.

Disk Utility

Open Applications > Utilities > Disk Utility.

Select the drive you want to examine on the left (red arrow). Be sure to select the drive, not the container that holds the drive.

Choose View > Show APFS Snapshots.

Open the window a bit to see a list of all snapshots and their sizes (red arrow). Ignore Tidemark, Size is the important column.

Select one or more snapshops – I recommend deleting those that are the oldest – and click the minus button (red arrow).

Poof! Instant free space.

Carbon Copy Cloner

Open Carbon Copy Cloner and click the Volumes text button in the top left.

Select the volume you want to examine; Thunderblade in my case.

On the right is a list of all snapshots contained on it.

Click the Size column header to sort them in order by size. (Not required but good to know.)

Highlight the ones you want to delete, then press the Delete key.

I recommend deleting oldest files first, while making sure to keep those which are most recent. Anything APFS really needs, it will rebuild.

Either way, this is a fast way to recover storage space that you thought you’d lost.

EXTRA CREDIT

Here’s an Apple support document from Apple that provides more details.

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