MacBook Air 2013 SSD capacity?

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Level 1

5 points

MacBook Air 2013 SSD capacity?

Hi all,

I just received my new MacBook Air 13" w/8gb. I was a bit confused when the total size of the Macintosh HD is reported as approx 121gb. My 2009 MacBook Pro was upgraded to a 128gb SSD (OCZ Vertex 4, IIRC) and the system reports it as a full 128gb.

I've read the support article here http://support.apple.com/kb/ts2419. I understand for a few releases of Mac OS they're now reporting the GB size in 1000-byte segments, rather than 1024-bytes. This still wouldn't explain it fully as I'd expect a 128gb drive to appear as ~119gb with 1024 byte units, not 121gb.

Is it expected behaviour that it displays a smaller amount of storage on the SSD? Why didn't the third-party SSD do this?

MacBook Air, OS X Mountain Lion (10.8.4), mid-2013, 13" w/8gb

Posted on Aug 9, 2013 5:00 AM

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Answer 1

Zane W

Level 3

670 points

Aug 12, 2013 2:45 PM in response to creepynut

According to the aricle you came from:

Understanding storage capacity in Solid State Drives and Flash Storage

Storage capacity displayed in Disk Utility by for Solid State Drives and Flash Storage will show a slightly smaller size. For example, a 256 GB Solid State Drive (SSD) should have a total of approximately 250 GB.

These items may account for the additional space used in your Solid State drive and Flash Storage:

EFI Partition
Restore Partition
Wear-leveling blocks
Write-buffer area
Metadata
Spare blocks
Grown bad blocks
Factory bad blocks

This may or may not apply to 3rd party SSDs depending on the onboard controllers that they use.

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Answer 2

Aug 12, 2013 3:00 PM in response to creepynut

creepynut

I just received my new MacBook Air 13" w/8gb. I was a bit confused when the total size of the Macintosh HD is reported as approx 121gb.

Normal. .Exactly the same as mine...121 Free + 6+ gigs plus of OSX files, and Applications , drivers, etc etc. 😊

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Answer 3

LowLuster

Level 6

12,105 points

Aug 12, 2013 3:14 PM in response to creepynut

I would say the drive, SSD, itself has a total of 128GBs available and then they save, block out, 7GBs (or there abouts) for fault provisioning. So if one of the chips fail (chips is not the right term) the drive electronics start using the blocked out area.

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Answer 4

creepynut Author

Level 1

5 points

Aug 12, 2013 5:34 PM in response to Zane W

That's true the article says that. I should have been more clear, I'm wondering why my OCZ SSD showed the full capacity and this one doesn't.

I'm beginning to suspect OCZ does one of 2 things - either they reserve additional space above the 128gb advertised for wear levelling, or they simply don't reserve space and when it's gone it's gone.

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Answer 5

creepynut Author

Level 1

5 points

Aug 12, 2013 5:35 PM in response to LowLuster

@PlotinusVeritas, I don't believe this is the case. Disk Utility reports the full disk size as 121gb, I believe the OS files are in this, not the 121-128 space (if this were the case I'd have no complaints).

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Answer 6

Aug 12, 2013 5:57 PM in response to creepynut

Available on a new out of box should read 121, plus or minus. I assume correctly yours reads 121 AVAILABLE correct.

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Answer 7

adml

Level 1

0 points

Aug 12, 2013 6:58 PM in response to PlotinusVeritas

I just purchased a 2013 MacBook Air, 4gb/128gb. It's showing Capacity as 120gb, not Available as that number. Is this what should be showing, +/- any normal variance, or does it indicate a problem ? Thanks.

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Answer 8

Aug 12, 2013 7:17 PM in response to adml

Normal, ....Yes, 120+/- gig Capacity,...

121/120 Free + 6+ gigs plus of OSX files, Applications , drivers,......and dont forget the recovery

Yes, your new in box should show 120 +/- capacity

Here is a picture of my Air in disk utility, showing 87.9 GIg available.., of which Ive already thrown 33gigs of my own APPS and personal files onto the SSD, on top of the resident OSX files, drivers, resident APPs, ...and the recovery.

33my own stuff + 7gig +/- resident already in place new out of box + 88gig available (my Air) = 128Gig 😉

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Answer 9

adml

Level 1

0 points

Aug 12, 2013 7:18 PM in response to PlotinusVeritas

Thank you for the quick response !

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Answer 10

LowLuster

Level 6

12,105 points

Aug 13, 2013 12:37 AM in response to PlotinusVeritas

Capacity is the Total amount of disk space available before any files are counted. Apple either needs to update their specs or start using a different SSD that includes space above their specs for over-provisioning.

All SSDs have an area set aside for fault tolerance. The newest Crucial M500 are rated at 240GBs but they actually have 256GBs of flash storage. The extra 16GBs that isn't listed in their specs it for this fault tolerance, over-provisioning.

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Answer 11

creepynut Author

Level 1

5 points

Aug 22, 2013 8:25 AM in response to LowLuster

I agree. Capacity should be the total space the drive has. The OS is installed within this capacity.

My 2009 MacBook Pro had a 160gb HD. Disk Utiltiy showed a 160gb capacity.

I upgraded the 2009 MacBook Pro to a 128gb OCZ SSD. Disk Utility showed a 128gb capacity.

Bought a 2009 MacBook Air with a 128gb SSD. Disk Utility shows ~120gb capacity.

This is why I created the thread. The extra 7-8gb space "above" the 120gb isn't used by the OS. The OS is installed on the Macintosh HD partition (which is only 120.47gb). You can see the space taken from the recovery partition (in PlotinusVeritas's screenshot, 121.33 APPLE SSD on the left, the Macintosh HD Partition is 120.47 = 0.86gb used by the recovery partition).

Very disappointed in Apple here.

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