Brand new MBA 20GB missing off the SSD

patch5674 · Jul 29, 2011

Hi there guys, I was wondering if you any of you could she dome light on this....I have a brand new 2011 MBA with a 128GB drive. I go into system profiler and it says 107 GB available of a possible 120GB which i understand that the OS needs room etc, But I still don't get where those 13 other GB's have gone is says 3 GB of apps which i assume is ilife etc because this MBA is completely clean at the moment. but it has 9.5 GB categorised as "other"

So basically i was wondering if anyone could tell me what exactly is covered by the "other" category and why so much of my SSD's room is taken on a blank laptop fresh out of the box.

Regards.

xxmacbethxx · Jul 30, 2011

sometimes hdd makes will mark there hdd drives off a different scaling procedure then what is typically used i have seen them use 1000bytes compared to the 1024 to make a kilobyte. that can knock down the room a little bit to.

Dysfunction · Jul 30, 2011

You're (xxmacbethxx) referring to a base 10 and base 2 difference. Briefly put, marketing sells drives using base 10, but computers (historically) calculate in base 2 (binary). On a 120GB hard drive, this really should show somewhere around 112GB or so in base 2 calculation (please don't make me really do the math tonight), due to this. Keep in mind this is SOLELY a difference in how the bytes are calculated into easier to express components.

You can see this on my system with a 500GB hard drive. First in base 10, then base 2, then in the actual 512byte blocks the system uses.

Code:

mikeMBP:/ mike$ df -H |grep disk0s2 |awk '{print $2}'
500G
mikeMBP:/ mike$ df -h |grep disk0s2 |awk '{print $2}'
465Gi
mikeMBP:/ mike$ df -b |grep disk0s2 |awk '{print $2}'
976101344

Now with that all being said, 10.7 reports in base 10 out of the box. So this isn't the issue above. Your operating system is about 10GB of install space, out of the box. Much of this will probably be categorized as 'other'.

patch5674 · Jul 30, 2011

Ok I understand the different scaling methods but if 10.7 calculates in base 10 then why is it showing that the total disk space is 120GB on a 128GB drive?

Then there is a further 9.5GB taken off that in the "other" category.

Sorry if I may be making you repeat yourself but I expected to not be able to access a portion of the disk that held the OS but in my eyes 20GB missing is a bit much.

wytwolf · Jul 30, 2011

MAC's use to display the HD in binary and companies advertise in base 10. But since i believe leopard... definitely snow leopard OSX displayed capacities in base 10 also. My 500GB HD is displayed as 499.75, and my previous HD was 320 and reported in OSX as 320.20GB. Unless SSD's are reported differently then my internal or thumb drive (8GB reported as 8.2GB) then something is wrong.

Dysfunction · Jul 30, 2011

Ok, ya know.. now I'm curious. Go into Disk Utility please, select the disk and go to Partition. How big does the drive show in there? (I'm not sure yet about the nifty GUI thing from iTunes in About This Mac..)

There is, btw, some overhead for formatting. But I don't recall it being very much at all with an HFS+ format.

patch5674 · Jul 30, 2011

Yeah I shall post the disk utility info up after I get in from work.

I was thinking the exact same as you mate. When I went into about this mac I was pretty suprised. Not keen at all

bobtomay · Jul 30, 2011

128 GB is the raw NAND capacity. Most of the drives I've looked at only have 120 GB available to the user and some even less. (Don't ask me, I don't know why. Haven't gotten into SSD that much yet. Only know what I see in the reviews - like this one at AnandTech.

So the op has 120GB of user available space. The OS and all the apps installed take up approx. 13 GB, no mystery there. Takes up the same 13 GB on my Air, and the same 10 GB on anyone's machine with a fresh install of Lion. I got the 256 GB version and it has 251 GB available to the user - the EFI and Lion restore partitions take up a total of 1 GB leaving me 250 - before installing Lion.

Dysfunction · Jul 30, 2011

Ahhhh I forgot about the NAND over-provisioning. This really has to do with performance. That said, I disagree with including this over-provisioned amount in the total storage as-sold. It should be sold as available user storage IMO.

Micron's got a good explanation..

Micron Innovations Blog » Overprovisioning: Give a little, get a lot.

patch5674 · Jul 30, 2011

So this looks pretty normal to you guys, thanks to the NAND provisioning?

Whilst i get what is going on here it is mildly annoying, I took into account about 8-10GB being missing for the OS and ilife etc i wasn't quite expecting that much. But oh well as long as it is a normal thing and not just my MBA i guess ill have to suck it up.

Thanks for all the swift replies guys.

Dysfunction · Jul 30, 2011

Yep, with the provisioning taken into account it looks completely normal.

harryb2448 · Jul 30, 2011

Not sure of this disk usage with an SSD. For example have a Mercury Extreme with 60.2GB capacity and Disk Utility shows 59.16GB available, and adding the Available and Used together comes to this 59.16GB so it would seem formatting etc uses only just over 1GB space, not 10GB or 20GB or any other figure. And under 'Partition' the amount shown is also 59.16GB.

Dysfunction · Jul 30, 2011

Each SDD manufacturer reports differently. Some will build theirs to report ONLY the amount available to the user (Micron/Crucial do this) and effectively hide their over-provisioned slice. Others, do not.