PDA

View Full Version : 120GB on a 128GB Air?




altecXP
Nov 27, 2011, 11:46 AM
I know the Recovery drive takes up 650MB, but where is the other 7.25GB?



wrinkster22
Nov 27, 2011, 11:48 AM
I know the Recovery drive takes up 650MB, but where is the other 7.25GB?

OS. read the box "Capaicity is formatted for less" An 8gb iPhone is actually only 6gb,

altecXP
Nov 27, 2011, 11:51 AM
Yes, but OS X Lion tends to show the full size. It does with my other SSD's and HDD's

Mlrollin91
Nov 27, 2011, 12:53 PM
128GB is really only 128,000,000,000 bytes instead of 137,000,000,000 bytes. So the actually drive is only roughly 124GB after conversion. Minus OS and Recovery drive bring it down to 120ish.

Edit: After rechecking my math, 120GB is just over 128,000,000,000 bytes.

altecXP
Nov 27, 2011, 01:31 PM
128GB is really only 128,000,000,000 bytes instead of 137,000,000,000 bytes. So the actually drive is only roughly 124GB after conversion. Minus OS and Recovery drive bring it down to 120ish.

Edit: After rechecking my math, 120GB is just over 128,000,000,000 bytes.

Yes, but Lion, and I think SL, use 1000 not 1024

KPOM
Nov 27, 2011, 01:47 PM
Yes, but Lion, and I think SL, use 1000 not 1024

True, but SSDs are quoted based on their absolute size, which includes amounts that the controller sets aside for low level operations such as overprovisioning, wear leveling, and garbage collection (i.e. not available for data storage). The actual capacity of the 128GB SSD is about 121GB, while the 256GB capacity is actually about 250GB using the base 1000 system.

johnhurley
Nov 27, 2011, 02:00 PM
I know the Recovery drive takes up 650MB, but where is the other 7.25GB?

Overhead and rounding off and formatting and SSD stuff ...

FrancoisC
Nov 27, 2011, 02:03 PM
Must depend on the manufacturer, my intel 600GB show as 600 in sl/lion

komoornik
Nov 27, 2011, 02:36 PM
True, but SSDs are quoted based on their absolute size, which includes amounts that the controller sets aside for low level operations such as overprovisioning, wear leveling, and garbage collection (i.e. not available for data storage). The actual capacity of the 128GB SSD is about 121GB, while the 256GB capacity is actually about 250GB using the base 1000 system.

The actual usable capacity of the 128 GB SSD in MBA is 113 GB.

Apple is messing around a bit. They say 128 GB, but they don't count space taken for wear leveling etc.

Coz for example Crucial M4 128 GB got actually over 119 GB of usable space.

And Sandforce based drives already are sold as 120 GB not 128 GB, coz they really are a bit "smaller".

altecXP
Nov 27, 2011, 03:48 PM
Ah I didn't realize that they didn't count the wear leveling space. That totally makes sense now.

Mlrollin91
Nov 27, 2011, 05:21 PM
Yes, but Lion, and I think SL, use 1000 not 1024

That was my point. 1024 would be 137,000,000,000 bytes for 128GB. 128,000,000,000 would be 1000 for 128GB, but when you then use the formula, 128,000,000,000 bytes is truly 120ishGB.

rbrian
Nov 27, 2011, 10:46 PM
Yes, but OS X Lion tends to show the full size. It does with my other SSD's and HDD's

I agree. After I installed Lion on my Pro, my hard drive capacity went from 931Gb to 1000Gb. At the same time, a 679Mb ISO wouldn't fit on a 700Mb CD, saying it needed 720Mb. Don't you just love standards? There are just so many to choose from! In practice though, you should keep about 10% of your storage capacity free, so it's all moot.