HDD total capacity, used and free space not matching

[JulienFranc]

Hello everyone, 

I connected an external drive to my iMac. Initially it was not recognized (it read: Error 49153 unable to mount the disk, 500 gb total capacity, 500 gb free space). I formatted it, and now it works and I copied a folder (17 gb) on it, but now it reads: 500 gb total capacity, 493 gb free space, 17 gb used. Why is it not showing 483 gb of free space instead? Thank you in advance

[Kon-Tiki]

You are seldomly going to get the advertised capacity out of a drive, for instance due to formatting overhead and spare sectors (this applies to both HDDs and SSDs). This would explain why it says 500 GB total and 493 GB free when it is empty. As to why it doesn't show the reduced space after copying a file to it I'm not sure. My guess would be that maybe macOS only updates the free drive space information every couple of minutes or so.

Just try waiting some time or re plug your drive to see whether this solves the free capacity problem.

[JulienFranc]

44 minutes ago, Kon-Tiki said:

You are seldomly going to get the advertised capacity out of a drive, for instance due to formatting overhead and spare sectors (this applies to both HDDs and SSDs). This would explain why it says 500 GB total and 493 GB free when it is empty. As to why it doesn't show the reduced space after copying a file to it I'm not sure. My guess would be that maybe macOS only updates the free drive space information every couple of minutes or so.

Just try waiting some time or re plug your drive to see whether this solves the free capacity problem.

I'm sorry, maybe I wasn't clear enough, but here I'm having the opposite behaviour: it *seems* like the drive is 10 gb bigger than advertised (493+17=510)

[Kon-Tiki]

As I've mentioned:

21 hours ago, Kon-Tiki said:

As to why it doesn't show the reduced space after copying a file to it I'm not sure. My guess would be that maybe macOS only updates the free drive space information every couple of minutes or so.

Just try waiting some time or re plug your drive to see whether this solves the free capacity problem.

That's my guess. Since some time has passed: Did you check whether, after re-plugging your drive, the capacity is shown correctly now?

[JulienFranc]

Nope. But trying on other machines gives 483 gb of free space as expected, instead of 493. Not sure exactly where is the issue, but it's not a big one, guess I'll live with it.