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miggitymac
Nov 27, 2010, 08:11 PM
So, I had to exchange my 13.3 MBA and got its replacement last week. Before I sent the first one back I wiped the SSD and the Disk Utility showed that it's capacity was ~128 GB.

Well I got the replacement MBA and this one is reading that my capacity is ~120 GB. To be clear, this is not my current capacity of the drive...it's the total capacity.

Can someone explain to me why I don't have the full 128 GB that Apple advertises?

I remember there was an early thread about this topic that was posted about the time that the new MBAs were first released, but 3 MRGoogle attempts didn't get me the thread I was looking for. :(

Any input would be appreciated!



teski
Nov 27, 2010, 08:15 PM
No hard drive is exactly what they state it to be. My 256GB drive shows 250.66 max. This is an age old thing with any hard drive.

ZenErik
Nov 27, 2010, 08:18 PM
Differences with formatted capacity? I have a 128 GB in my MBP, but it only reads as 120 GB. Which is fine since I only use 28 GB. All the free space is great since I use this thing for sound recording and don't want to wear down my SSD too quickly anyway.

miggitymac
Nov 27, 2010, 08:31 PM
Update:

Ok, fourth MRGoogle attempt ftw!

http://forums.macrumors.com/showthread.php?t=1042562

But after reading that entire thread I'm still a bit confused as to why one MBA would show 128 GB, and another one of the same model shows 120 GB. I assume they're using the same make and models of SSDs....

Is it really as simple as saying:

No hard drive is exactly what they state it to be. My 256GB drive shows 250.66 max. This is an age old thing with any hard drive.?

r6girl
Nov 27, 2010, 08:44 PM
It sounds like they gave you one with a standard hard drive instead of an SSD. You don't mention which generation MBA you have but the Rev. B models came with a 120 GB hard drive OR a 128 GB SSD.

miggitymac
Nov 27, 2010, 08:46 PM
It sounds like they gave you one with a standard hard drive instead of an SSD. You don't mention which generation MBA you have but the Rev. B models came with a 120 GB hard drive OR a 128 GB SSD.

Oh, sorry, I forgot to mention that it's the new 2010 MBA, 13.3 inch, 128 GB (supposedly) SSD, 4 GB RAM.

I don't think they could fit a standard HD in these MBAs :D

jimboutilier
Nov 27, 2010, 09:01 PM
It depends on which utility you ask about space.

Mass storage manufacturers routinely lie about space by calculating 1k as 1000 bytes rather than 1024. That adds up when you are talking hundreds of gigabytes. if you read the fine print they disclose this fact.

Until snow leopard most OSs correctly reported capacity so your 128gb hard drive or SSD would show up as 120gb or so when you factor in formatting overhead, and 1000 vs 1024.

With show leopard Apple in it's infinite wisdom decided to use the mass storage definition of a "k" in some places so a 128gb drive would show up as 128gb in some places and unfortunately as about 120 in others so it added to confusion rather than reducing it.

I think the idea was to stop the questions like why is my 128gb drive only 120gb? The problem was it caused difficulties when talking about bytes used vs bytes free vs capacity and gives people an inaccurate view of their storage.

So if you look in various places in snow leopard you'll get different numbers and it's not that one machine was different than the other, it's where you happened to look.

bdavis89
Nov 27, 2010, 09:02 PM
Are you sure the sides are correct? I was at my local best buy and they had a 13inch and 11inch MBA set up next to each other. I played with the 13in for 10 minutes, cause thats the one i'm interested in, and only when I was just leaving did I realize that it was an old MBA with the little drop door for the USB. They look and feel pretty much the same!!

miggitymac
Nov 27, 2010, 09:08 PM
It depends on which utility you ask about space.

Mass storage manufacturers routinely lie about space by calculating 1k as 1000 bytes rather than 1024. That adds up when you are talking hundreds of gigabytes. if you read the fine print they disclose this fact.

Until snow leopard most OSs correctly reported capacity so your 128gb hard drive or SSD would show up as 120gb or so when you factor in formatting overhead, and 1000 vs 1024.

With show leopard Apple in it's infinite wisdom decided to use the mass storage definition of a "k" in some places so a 128gb drive would show up as 128gb in some places and unfortunately as about 120 in others so it added to confusion rather than reducing it.

I think the idea was to stop the questions like why is my 128gb drive only 120gb? The problem was it caused difficulties when talking about bytes used vs bytes free vs capacity and gives people an inaccurate view of their storage.

So if you look in various places in snow leopard you'll get different numbers and it's not that one machine was different than the other, it's where you happened to look.

Well, like I said, before I shipped the first one back I used Disk Utility to wipe the SSD clean and it reported ~128 GB. Finder also showed about 100 GB of free space...I kept track of it because I planned to use Monolingual and see how much space it would free up.

With the replacement, Disk Utility is showing ~120 GB (I noticed when I went in to repair permissions) and Finder is showing ~92 GB of free space.

I did a restore from Time Machine backup so I have the exact same apps and files on the replacement as I did on the first MBA.

Btw - Monolingual didn't save much space at all...well, not as much as I was anticipating.

miggitymac
Nov 27, 2010, 09:10 PM
Are you sure the sides are correct? I was at my local best buy and they had a 13inch and 11inch MBA set up next to each other. I played with the 13in for 10 minutes, cause thats the one i'm interested in, and only when I was just leaving did I realize that it was an old MBA with the little drop door for the USB. They look and feel pretty much the same!!

Yes I'm sure this is the new MBA...the About This Mac section confirms that I have 4 GB of RAM and an 9CDF display. I also don't have backlit keys...;)

robeddie
Nov 27, 2010, 09:16 PM
Yes I'm sure this is the new MBA...the About This Mac section confirms that I have 4 GB of RAM and an 9CDF display. I also don't have backlit keys...;)

You've got a 128 ssd. 8 gigs is reserved for failure rates. then you have to subtract the difference between 120 and real formatting, which will result is around 113 gigs available before any system install. This has been gone over countless times in the past 4 years.

miggitymac
Nov 27, 2010, 09:20 PM
You've got a 128 ssd. 8 gigs is reserved for failure rates. then you have to subtract the difference between 120 and real formatting, which will result is around 113 gigs available before any system install. This has been gone over countless times in the past 4 years.

I did do the research and linked a thread that discusses it. But like I said, nothing in that thread can explain why the same model of SSD running on the same OS and computer would report differing capacities...

teski
Nov 27, 2010, 09:33 PM
I did do the research and linked a thread that discusses it. But like I said, nothing in that thread can explain why the same model of SSD running on the same OS and computer would report differing capacities...

Please don't take this the wrong way, but could it be possible that you misread the total capacity on your other MBA? I've never seen the total drive space actually equal what's on the label whether or not that's an SSD, CF card, SD card, regular hard drive, etc. These are all theoretical but in the way the drive is sectored in bytes, it won't equal the total. I'm, quite frankly, far more surprised that you'd have one that showed 128 than the current one showing 120.

miggitymac
Nov 27, 2010, 09:49 PM
Please don't take this the wrong way, but could it be possible that you misread the total capacity on your other MBA? I've never seen the total drive space actually equal what's on the label whether or not that's an SSD, CF card, SD card, regular hard drive, etc. These are all theoretical but in the way the drive is sectored in bytes, it won't equal the total. I'm, quite frankly, far more surprised that you'd have one that showed 128 than the current one showing 120.

I'm pretty sure on this. Before I sent back the first MBA, I wrote down:
1) the serial number (to make sure that I was getting a new MBA and not just the same one after its been repaired).
2) the display model (the first one was 9CF0 and after reading some of the threads on these forums I wanted to see if there really was a difference b/w the 9CF0 and 9CDF...I didn't notice anything significant)
3) the amount of free space according to Finder (to see how much space I'd save by customizing the SL install and running Monolingual on the replacement MBA)

Also, as I mentioned before, I read the thread linked above and remember thinking that I was glad that I didn't have that problem. :p

I'm not bothered by this enough to exchange it again...the waiting period for the first exchange was painful enough.

I'm more just curious as to why it is as it is.

teski
Nov 27, 2010, 10:05 PM
I'm pretty sure on this. Before I sent back the first MBA, I wrote down:
1) the serial number (to make sure that I was getting a new MBA and not just the same one after its been repaired).
2) the display model (the first one was 9CF0 and after reading some of the threads on these forums I wanted to see if there really was a difference b/w the 9CF0 and 9CDF...I didn't notice anything significant)
3) the amount of free space according to Finder (to see how much space I'd save by customizing the SL install and running Monolingual on the replacement MBA)

Also, as I mentioned before, I read the thread linked above and remember thinking that I was glad that I didn't have that problem. :p

I'm not bothered by this enough to exchange it again...the waiting period for the first exchange was painful enough.

I'm more just curious as to why it is as it is.

Ya, not sure what's up with it saying you really had 128. I did a few searches, and came across this thread that has some good detail for you on how the manufacturers calculate things vs. operating systems. http://www.tomshardware.com/forum/245851-32-hard-disk-label-actual-capacity-difference-excessive

aristobrat
Nov 27, 2010, 10:22 PM
I'm more just curious as to why it is as it is.
Me too. Like someone else mentioned, SSDs reserve a certain amount of drive space as reserves to account for when existing areas on the drive can't be written to anymore, but you would think that amount would be consistent amongst similar drives.

Be curious to see what other 128GB drive owners are seeing.

Over Achiever
Nov 27, 2010, 10:34 PM
In Finder: 120.99 GB (Macintosh HD)
In Disk Utility: 121.33 GB (Includes a 209.7 MB partition)

mrsir2009
Nov 27, 2010, 10:45 PM
Yeah, it is just a hard drive thing. Even on memory sticks its not unusual to have a few MBs missing... However I have found that reformating the disk works :D

Thiol
Nov 28, 2010, 04:35 AM
Please don't take this the wrong way, but could it be possible that you misread the total capacity on your other MBA? I've never seen the total drive space actually equal what's on the label whether or not that's an SSD, CF card, SD card, regular hard drive, etc. These are all theoretical but in the way the drive is sectored in bytes, it won't equal the total. I'm, quite frankly, far more surprised that you'd have one that showed 128 than the current one showing 120.

+1 I haven't heard of anyone else at all that has reported seeing 128 GB in Disk Utility.

KnightWRX
Nov 28, 2010, 11:09 AM
I'll quote the relevent posts from past threads, since again I see people trying to say it's things like "Formatting" or "1024 vs 1000 kbytes" (it's not, it's SSD overprovisioning) :

Too many people replying above misunderstanding the issue. Yes, all SSDs have some element of over provisioning otherwise they would quickly slow down, with or without TRIM.

As a rule of thumb, if an SSD drive is advertised as 64GB, then expect 60GB. Others, like OCZ are a bit more honest and state the capacity as 60GB although clearly more has been placed on the drive for provisioning.

Whether the capacity overstatement is down to Apple or the flash memory manufacturer is anyone's guess.

Seriously, all the people bashing the OP have no clue. This isn't the GiB to GB conversion, you are getting less space. Have you guys even bothered to look at your partition ?

In GiB :
$ df -h /
Filesystem Size Used Avail Capacity Mounted on
/dev/disk0s2 113Gi 68Gi 44Gi 61% /

In GB :
$ df -H /
Filesystem Size Used Avail Capacity Mounted on
/dev/disk0s2 121G 73G 48G 61% /

So the drive is not a 128GB drive, it's a 121 GB drive, at least according to the partition. If we look at the disk, the partition is made using the entire sector count, give or take 1, which doesn't amount to 7 GB :

$ sudo fdisk /dev/disk0
Password:
Disk: /dev/disk0 geometry: 14751/255/63 [236978176 sectors]
Signature: 0xAA55
Starting Ending
#: id cyl hd sec - cyl hd sec [ start - size]
------------------------------------------------------------------------
1: EE 1023 254 63 - 1023 254 63 [ 1 - 236978175] <Unknown ID>
2: 00 0 0 0 - 0 0 0 [ 0 - 0] unused
3: 00 0 0 0 - 0 0 0 [ 0 - 0] unused
4: 00 0 0 0 - 0 0 0 [ 0 - 0] unused

Finally, system profiler reports the drive as a 121 GB drive :

APPLE SSD TS128C:

Capacity: 121.33 GB (121,332,826,112 bytes)
Model: APPLE SSD TS128C

So everyone bashing the OP : you guys are wrong, he is right.

KPOM
Nov 28, 2010, 11:44 AM
I'm not sure why the first drive reported 128GB. SSDs are always less than the advertised capacity because of "overprovisioning." Basically, the controller sets aside a certain percentage of the drive as "free space" so that it doesn't constantly read and write the same area or leave "garbage" throughout the drive. It has to do with the way SSDs delete files. A computer doesn't actually erase a deleted file. It just marks the space as free to be overwritten. However, it's quicker for an SSD to write to free space than to overwrite existing space, and so traditional deletion techniques can slow down an SSD drive over time.

Without overprovisioning, the drive starts to slow down even faster. There is a way to "recondition" drives, and Windows 7 uses something called TRIM to slow down the degradation in drive performance. OS X does not currently support TRIM, so it's possible that Apple used a drive with higher overprovisioning.

miggitymac
Nov 28, 2010, 01:54 PM
I'm not sure why the first drive reported 128GB. SSDs are always less than the advertised capacity because of "overprovisioning." Basically, the controller sets aside a certain percentage of the drive as "free space" so that it doesn't constantly read and write the same area or leave "garbage" throughout the drive. It has to do with the way SSDs delete files. A computer doesn't actually erase a deleted file. It just marks the space as free to be overwritten. However, it's quicker for an SSD to write to free space than to overwrite existing space, and so traditional deletion techniques can slow down an SSD drive over time.

Without overprovisioning, the drive starts to slow down even faster. There is a way to "recondition" drives, and Windows 7 uses something called TRIM to slow down the degradation in drive performance. OS X does not currently support TRIM, so it's possible that Apple used a drive with higher overprovisioning.

Yea, that is weird. If I hadn't purposely kept track of the amount of storage I had on it, I would start to second guess myself.

I guess I'll just consider myself lucky since it sounds like the SSD on the first MBA would have degenerated faster than the one I have now.

Thanks for the comments everyone.

r6girl
Nov 28, 2010, 06:05 PM
Oh, sorry, I forgot to mention that it's the new 2010 MBA, 13.3 inch, 128 GB (supposedly) SSD, 4 GB RAM.

I don't think they could fit a standard HD in these MBAs :D

Ah. Thanks for the clarification. Congrats on the new MBA, BTW!

FWIW, I have a rev. B MBA with a 128 GB SSD and its capacity is listed as 121.33 GB in Disk Utility (and I've never given it a second thought :p ).