Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

whozurdaddy

macrumors newbie
Original poster
Feb 4, 2008
14
0
Are we getting short changed? On Apple's site (http://www.apple.com/macbookair/specs.html) for the Optional 64GB solid-state drive at the bottom of the page it states that "1GB=1 billion bytes. Actual formatted capacity less."

So by this math, 64GB = 64,000,000,000 bytes. If you convert that gigabytes it should be 59.6GB. Why is the capacity in Disk Utility showing 55.5GB? Is this a 60GB SSD drive? I know people have complained about similar issues before (see here: http://forums.ilounge.com/archive/index.php/t-132092.html) but I don't understand the 4GB discrepancy (59.6GB vs 55.5GB).
 

switz

macrumors 6502a
Jan 16, 2008
505
521
East edge of Phoenix urban sprawl
I am typing this on my new 1.8 SSD I bought at the Chandler Apple store in Phoenix. It was the last of the ten units that came in today. The 64Gb is probably a marketing number. One typically looses at a minimum of 7% to 15% of the space when formatting the device. If we do the division, we see about 13% overhead which is not that unreasonable.

The unit I had on order with the Apple store may not get out of Shanghai Pudong airport may not depart until next week due to both the Chinese New Year celebrations and the severe weather. As I will on the road, I elected to acquire the available unit. One in hand is worth two in the bush.

In the time it took to type this the little fan has come on. I think it has been busy downloading updates while I was composing this message.
 

whozurdaddy

macrumors newbie
Original poster
Feb 4, 2008
14
0
First, congrats on your new system! I ordered mine from apple.com and it cleared customs on 2/3. I have yet to hear my fan come on, but I'm not really doing a whole lot yet.

As for the space, 64GB is a marketing number but even using their math it doesn't add up. I understand slack space and how cluster sizes can affect the available free space, but we're talking about the raw numbers from Disk Utility.

It's all math. We should be able calculate exactly how much raw disk space is available and by numbers, it's off my 4GB.
 

michaelvoigt

macrumors member
Nov 13, 2007
60
0
Austin,TX
lost space could be Mac OS X swap partition

Does OS X use a dedicated swap partition? if that is the case that could account for the lost space that you see?
 

jahala

macrumors regular
Feb 7, 2008
206
15
Efi

I know that there is a small partition for EFI data, but I don't know how big it is.
 

aristobrat

macrumors G5
Oct 14, 2005
12,291
1,397
Yeah, that's true. When I googled this topic, I saw an HP document that stated up to 8GB on a SSD drive could be dedicated to system recovery, so I wasn't sure if they were specifically talking about how they do SSD drives, or SSD drives in general.

This was interesting. I wasn't aware that there was a maximum amount of times that a SSD could be written to (not that a normal person would ever run into that). Wonder if there's some disk space kept in reserve for problems with cells?
There’s also some concern about the drive wearing out. You may not know it but flash memory has a limited amount of times that you can write to it. With my old Omnibook 300, I had to occasionally run wear leveling software to ensure that there weren’t premature dead cells occurring. Those dead cells would stop responding to write commands. While you could read from them forever, the cells would essentially turn into read only memory. That still occurs on flash memory today but the algorithms to minimize it and the cycles has increased so much that it really isn’t a factor. In the MTron’s case, the company claims a write endurance of greater than 140 years with you writing or erasing 50GB per day. If true, that means the notebook will long be in the scrap pile before you ever wear out any cells.
http://www.maximumpc.com/article/is_a_solid_state_drive_in_your_future?page=0,1
 

Krevnik

macrumors 601
Sep 8, 2003
4,094
1,301
This was interesting. I wasn't aware that there was a maximum amount of times that a SSD could be written to (not that a normal person would ever run into that). Wonder if there's some disk space kept in reserve for problems with cells?

All good drives do. Even HDDs you buy now have reserve blocks which are only used when bad blocks are found. But it doesn't affect the actual formatted capacity (The advertised space for an HDD doesn't include the reserve blocks).

I don't know why there is still a 4GB block of space unaccounted for. That is a bit big to be used for reserve blocks.
 

cowm007

macrumors regular
Feb 2, 2005
195
0
Open up terminal and type in "diskutil list". Maybe there's a hidden partition in there?
 

redbma

macrumors newbie
Oct 1, 2002
3
0
Have the same 'issue' here. Got my 1.8/64SSD MBA yesterday and noticed the reduced capacity. Diskutil results were:

/dev/disk0
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *55.9 Gi disk0
1: EFI 200.0 Mi disk0s1
2: Apple_HFS Macintosh HD 55.6 Gi disk0s2


Doesnt seem to shed any more light on where the missing 4GB ended up.

Anyone tried doing a reformat and reinstall?
 

txlef

macrumors newbie
Feb 8, 2008
1
0
My diskutil list shows the same thing:

#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *55.9 Gi disk0
1: EFI 200.0 Mi disk0s1
2: Apple_HFS Macintosh HD 55.6 Gi disk0s2

I'm feeling kind of ripped off.
 

cowm007

macrumors regular
Feb 2, 2005
195
0
Yea, looks like the actual disk is 55.9 gb and not just the system partition. Diskutil's output indeed shows that the disk is just 56gb, so there's no hidden OS partition or anything (Also unlikely since a Leopard install disk is around 7gb).

For comparison purposes, I have a 500GB hard drive, but the actual size is about 465GB which makes sense once you do the math:
Marketing GB = 1,000,000,000 bytes
Real GB = 1,073,741,824 bytes (1024 B in a KB, 1024 KB in a MB, 1024 MB in a GB)

Marketing Capacity = 500,000,000,000 bytes
Real capacity = 465,660,000,000 bytes (500,000,000,000 / 1,073,741,824)

So 56gb from 64 is kinda sketchy. Especially when you're paying such a premium for the SSD drive. Why must they continue with these B.S. games of 1000 vs 1024 bytes to describe sizes?
 

acfusion29

macrumors 68040
Nov 8, 2007
3,128
1
Toronto
So Safari, Mail, iChat, Calendar, iTunes etc. are supposed to take up no space? :rolleyes:

That 4GB went towards the OS and the Apps installed.
 

cowm007

macrumors regular
Feb 2, 2005
195
0
So by this math, 64GB = 64,000,000,000 bytes. If you convert that gigabytes it should be 59.6GB. Why is the capacity in Disk Utility showing 55.5GB? Is this a 60GB SSD drive? I know people have complained about similar issues before (see here: http://forums.ilounge.com/archive/index.php/t-132092.html) but I don't understand the 4GB discrepancy (59.6GB vs 55.5GB).

I hate to say it, but the drive's actual capacity would be quoted by the manufacturer as 60Gb instead of 64Gb when using the 1,000,000,000 bytes per gigabyte conversion. So something's definitely strange and worth calling Apple about.
 

whozurdaddy

macrumors newbie
Original poster
Feb 4, 2008
14
0
I've done a reinstall (using the sticky here). The starting capacity of the drive is 55.9 GB.

I really do think there's something to this. I posted a message on Apple here), but I didn't really get anywhere.
 

ayeying

macrumors 601
Dec 5, 2007
4,547
12
Yay Area, CA
I noticed this at the stores too. The MacBook Air's SSD drive is only 55.9GB, which is bascially a 60GB hdd (55.9GB usable)
 

whozurdaddy

macrumors newbie
Original poster
Feb 4, 2008
14
0
Good find Beliyaal!

It's definitely a different drive. My drive is listed as a MCCOE64GEMPP with a capacity of 55.9 GB and Anand's is a SAMSUNG PZA064 SSD with a capacity of 59.63 GB.



I'll call Apple tomorrow. I don't want to whine here, but this is BS. Every gig counts when you're talking about an SSD drive. I paid for a 64GB drive and Apple sold me a 60GB drive.
 

profiteor

macrumors member
Jan 31, 2008
44
0
From the Samsung Semiconductor info page on the MBA drive:

Drive Capacity
Unformatted Capacity 64GB
User-Addressable Sectors 125,045,424
Bytes per Sector 512

= 59.63GiB (powers of 2 GB, what your OS sees)

There's an Apple Diagnostic Test accessible via D at boot without using the DVD... but I'm sure that either lives in EFI or the EFI partition. Very small. Not 4GB. Makes me wonder if Apple implemented a 10% rewrite area, or something.

OS X does not use a swap partition.

Half tempted to hack into EFI and see what it thinks of the drive.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.