Disk size defugality on Macbook Air

I have a new MacBook Air with a 120 gb ssd.

Looking at the About your Mac, it says I have 65 gb available.

In finder, Macintosh HD shows to have 55 gb available.

Clicking on Info for the Macintosh HD gives me 81 gb available.

The Unix df command gives me 111 gb available (which can't be even close)

The Unix du command gives 91 gb.


I get the impression that the new SSDs have characteristics that confuse the normal spinning platter size utilities.

Unless Lion has greatly changed size from Snow Leopard, my out of the box usage should be around 50 gb with 70 gb available.

Insights, anyone?

The 120's going to be around 110 or so due to NAND over-provisioning.

for a good explanation see:
Micron Innovations Blog » Overprovisioning: Give a little, get a lot.

I know it still doesn't deal with the discrepancy.

I'm not really seeing the differences on my 256 GB MBA folks are reporting on the 128.

System Profiler (System Information on Lion) and Get Info both report the same thing.
(Guess they've had so many Windows users buying Macs they decided the name needed changing.)

Don't personally use terminal for anything that doesn't require it - but What Size reports an 18GB smaller drive size than the two above.

Yea, how much over-provisioning there is (and whether they include it in marketed size or not) is completely up to the manufacturer of the drive. Don't get me wrong, the over-provisioning is a good thing. I just think it's disingenuous to include it as 'usable' size as is inferred by marketing.

I'd check terminal, I don't use finder if I can avoid it, but I don't have an SSD.