Hard disk puzzle - where are the missing gigs?

[Mark F]

Running OS 10.5.8 and a 1 TB external drive.  I was surprised to see that Finder says that only 444 gigs are available which means that about 556 gigs have been used. But when I add up the folders listed by Finder for that drive,  it totals 354 gigs not 556  ??

When I do a "Get Info" on the drive this is the report:  capacity - 931;   available - 444;     used - 487

I suspect that the 1 TB theoretical capacity is reduced to 931 due to a 30g Windows partition and the internal requirements of the drive itself.  But the other numbers do not make sense to me.  Why does Finder say that I've used 488 gigs when the sum of the files is only 354?  

Is there a simple explanation, have I got a bad drive or what? Is there a way to determine which is correct?

Thanks for helping.

[Craddosk]

In short, there is a significant difference between 1 GB and 1 GBi. If you look on the drive's box, it will tell you the exact difference, but suffice to say, they are not equal.

This has resulted in drive manufacturers  advertising things in GBi, which shows up as larger than most computers compute it as. This is evident everywhere, Apple (to name A computer manufacturer) will advertise a 320GiB drive, but the amount available to the individual is actually a bit less. I believe this was changed in Snow Leopard.

As to your issue, the amount of the drive is 1TBi. This, in is actually 930 GB (or whatever the number you mentioned is). So, subtract from that the 30GB windows install you mentioned, plus everything for applications, cookies, saved documents, pictures, etc. And you should come up with the amount used. Overall, I wouldn't worry too much about it. Unless you start noticing folders/files on your computer that are not made by you (ex. porn), your not suffering an outsider using your computer. Likely, your just missing a folder with pictures, or software drivers, that occupies lots of room.

[Craddosk]

Oh, if your looking to free up space, use the Find function, and remove anything Garageband related. That's a few GB's. But yeah, just look on the box and it'll tell you that 1TB is not actually 1TB as seen on 10.5.8. Don't worry about it, your drive (from this perspective at least) is just fine.

[titan]

Actually, Craddosk has it a bit backwards.

GB is 1,000,000,000 bytes.
GiB is 1,073,741,824 bytes.

You're not missing anything. Hard drive manufacturers report drive sizes in GB while all software report drive sizes in GiB. The problem stems from software developers using GB when GiB is intended; the manufacturers have rightly been using KB/MB/GB/TB whereas the software developers have not.

So, 931 GiB equals 1,000 GB, which is the same as 1 TB.

[Craddosk]

Go with him. He's got the easier (and correct) version of what I wrote.

[francois]

Actually, Craddosk has it a bit backwards.

GB is 1,000,000,000 bytes.
GiB is 1,073,741,824 bytes.

You're not missing anything. Hard drive manufacturers report drive sizes in GB while all software report drive sizes in GiB. The problem stems from software developers using GB when GiB is intended; the manufacturers have rightly been using KB/MB/GB/TB whereas the software developers have not.

So, 931 GiB equals 1,000 GB, which is the same as 1 TB.

In Snow Leopard (10.6) Apple changed the way HD capacity is reported.
Here is the tech note:  http://support.apple.com/kb/TS2419

[feppe]

The problem stems from software developers using GB when GiB is intended; the manufacturers have rightly been using KB/MB/GB/TB whereas the software developers have not.

Hardly the case. 1,024 has been the multiplier since the invention of binary-based computers (2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, etc.). Hardware manufacturers using 1,000 multiplier is a pure marketing ploy to make things sound bigger than they actually are.

[francois]

…is a pure marketing ploy to make things sound bigger than they actually are.

True but the ploy works fantastically well as I get that HD capacity question at least once a week...

[Mark F]

OK, I understand how a 1 TB drive really translates into a lot less available space. But I still do not get why the Finder tells me that I've used 488 gigs, a "Get info" on the drive tells me the same, but when I add up the space used by each of the listed folders it only comes to 354 gigs.  I've done this several times and it always comes out the same.

Where is the other 134 gigs? It can't be all cookies...

[titan]

OK, I understand how a 1 TB drive really translates into a lot less available space. But I still do not get why the Finder tells me that I've used 488 gigs, a "Get info" on the drive tells me the same, but when I add up the space used by each of the listed folders it only comes to 354 gigs.  I've done this several times and it always comes out the same.

Where is the other 134 gigs? It can't be all cookies...

Do you have a hidden folder that contains scratch, or something?

The other thing that comes to mind is that the method you're using to determine the folder size is reporting the total actual file size and not the file size on disk.

A disk is split into clusters. Only one file per cluster -- or multiple clusters -- is possible. So, you can have a drive with 4 KiB clusters with a 1 KiB file stored in that 4 KiB cluster. So, the actual file size is 1 KiB, but the file size on disk is 4 KiB. Or, you could have a 10 KiB actual file size that uses 12 KiB, three clusters, on disk. The problem is exacerbated with file fragmentation, but this is usually a negligible difference.

[francois]

OK, I understand how a 1 TB drive really translates into a lot less available space. But I still do not get why the Finder tells me that I've used 488 gigs, a "Get info" on the drive tells me the same, but when I add up the space used by each of the listed folders it only comes to 354 gigs.  I've done this several times and it always comes out the same.

Where is the other 134 gigs? It can't be all cookies...

Try to use a disk utility application such as the free OmniDiskSweeper (*). It'll tell you if you have hidden files/folders and their respective sizes.

(*)  http://www.omnigroup.com/applications/omnidisksweeper/

[Mark F]

Thanks for the reference to OmniDiskSweeper, its a useful program.  But nothing is ever simple. The first two listings were for 1.6TB of data, when the entire disk is only 1TB.  But the authors are very anxious to help out and when I emailed them they explained that the problem had to do with having TM backups on the disk.  It seems that TM does an incremental backup, linking back to earlier backups for the unchanged files. But the file size of the most recent backup shows as if everything was backed up.

I still haven't found my "missing" storage but I'm sure learning more about my hard drives than I knew before  

Mark

Try to use a disk utility application such as the free OmniDiskSweeper (*). It'll tell you if you have hidden files/folders and their respective sizes.

(*)  http://www.omnigroup.com/applications/omnidisksweeper/

[Kumar]

If your drive is partitioned with Windows, you could use TreeSize http://www.jam-software.com/treesize_personal/ to check what's on the drive.  There's a free 21 day trial.

Cheers,
Kumar

[nik]

Dear Mark,

If you want to see what files are hidden by OS X (this is for our simplicity and benefit according to apple) use these free apps;

1) IceClean from Macdentro www.macdentro.com. Once installed, look under the "Utilities" menu for an item called "Show and Hide Hidden Files and Folders" , then try adding up all your files/folders again to see if you get a number closer to what you're expecting.

2) Grandperspective - http://grandperspectiv.sourceforge.net/ - For a graphical representation of ALL the files on your HDD, the bigger the file the bigger the graphical representation. You'll find lots of interesting stuff with this one. Of note is the 'sleep' or hibernate file, it's typically the same size as the amount of RAM you have installed, in my case 4GB, it gets re-created after a reboot if deleted. You need this file!

Hope you find what you're looking for.

-Nik

Running OS 10.5.8 and a 1 TB external drive.  I was surprised to see that Finder says that only 444 gigs are available which means that about 556 gigs have been used. But when I add up the folders listed by Finder for that drive,  it totals 354 gigs not 556  ??

When I do a "Get Info" on the drive this is the report:  capacity - 931;   available - 444;     used - 487

I suspect that the 1 TB theoretical capacity is reduced to 931 due to a 30g Windows partition and the internal requirements of the drive itself.  But the other numbers do not make sense to me.  Why does Finder say that I've used 488 gigs when the sum of the files is only 354?  

Is there a simple explanation, have I got a bad drive or what? Is there a way to determine which is correct?

Thanks for helping.

[Mark F]

Thanks again guys. Hopefully the hidden files will be the difference.

[Tim May]

Actually, Craddosk has it a bit backwards.

GB is 1,000,000,000 bytes.
GiB is 1,073,741,824 bytes.

You're not missing anything. Hard drive manufacturers report drive sizes in GB while all software report drive sizes in GiB. The problem stems from software developers using GB when GiB is intended; the manufacturers have rightly been using KB/MB/GB/TB whereas the software developers have not.

So, 931 GiB equals 1,000 GB, which is the same as 1 TB.

This is very useful information. I never knew this.

Thanks a bunch.