[Cottonsworth]

I picked up an used mid-2011 MBA that is running 10.8 Mountain Lion. The previous owner did a reinstall of the OS but it doesn't seem to be a complete reinstall as there seems to be residue of previous files the previous owner had on.

Two questions:

1. This is the 256GB model but it only shows 210GB available. To make matters more confusing, the storage info box in about this Mac shows that movies take up 30GB, music 10GB, apps 12GB, photos 2GB and the rest are zero. If you add it all up, it exceeds the max cap of the SSD. (30 + 10 + 12 + 2 = 54, drive shows 256 - 210 = 46). There is a discrepancy of 8GB. But besides the discrepancy, I cannot locate any of these mystery movies/music, etc files. I did a pretty detailed search in finder that showed nothing. There are no additional users on the laptop.

Can any explain why there is a discrepancy and why such files are listed to exist? If so, where are they?

2. I read that you can reinstall the OS by holding down command + R during startup but you must be connected to the internet to do so. Are the reinstall files located on a partition on the computer or is it going to download it from the internet? I'm confused as why one needs to be connected to the internet in order to do this.

[Waragainstsleep]

If it has Mountain Lion, it will have a recovery partition which has enough on it to boot up and then download the ML installer from the App Store. It then reinstalls the OS from that file. This may not include any iLife Apps so if you haven't already downloaded them from the App Store, you might need to buy them again.

You can also get to the recovery partition by holding Alt when you boot.

[Gazoobee]

Originally Posted by Waragainstsleep 

If it has Mountain Lion, it will have a recovery partition which has enough on it to boot up and then download the ML installer from the App Store. It then reinstalls the OS from that file. This may not include any iLife Apps so if you haven't already downloaded them from the App Store, you might need to buy them again.

You can also get to the recovery partition by holding Alt when you boot.

Depending on how the previous owner had reinstalled the OS he/she might have wiped out the recovery partition. It sounds like they did a crap job whomever it was.

[Cottonsworth]

Thanks for the responses. Can anyone explain why there is a discrepancy in how the space is organized?

[I-ku-u]

Since the Storage info you refer to is likely inferred from stored Spotlight data, I'd say that the Storage/Spotlight data is just as out of sync as the rest of the disk from the previous owner's install attempt.

Anyway, it sounds like what you want is a complete disk wipe, not just a new OS install (the latter doesn't necessarily erase any data and by itself never erases all system data). Just run Disk Utility when you first boot from the install image, however you get it, and erase the disk. If that doesn't solve the problem, then the SSD is seriously wonky in some unexpected way.

[Cottonsworth]

Just finished a complete wipe. Things seem normal now, audio, movies, all that stuff shows zero. I have 239GB available now, I'm assuming the 11GB of taken space is the system files, although that seems a bit weird since I thought Mountain Lion takes up less than 5GB.

I'm happy with the way things are but my curiosity is just wondering why 11GB is taken instead of around 5GB. Anyone? Thanks.

[I-ku-u]

Well, my /System comes in at a little over 5GB, and then there's /Library, which represents the customizable/dynamic part of the OS. So, offhand, 11GB doesn't seem wrong.

If you really want to know how much your OS install is using instead of going from memory, either do 'Get Info' on those two folders or have finder's list view show and calculate all sizes for your boot disk to get those two sizes. This still isn't *all* of the data, just most of it, as it doesn't count hidden UNIX folders.

But since the discrepancy is already smaller than the conversion confusion that results by equating a GB as 1 billion bytes instead of 2^30 bytes, I wouldn't worry about it.

[Cottonsworth]

Thanks for the response. The only thing I'm missing now is the original iLife but the Apple Store said they'll put it back on for me. We'll see how that goes.