Prev: iTunes for all users?
Next: Who's connected to my computer?
From: rasberry on 9 Apr 2006 11:44
I have a 15" iMac, Machine Model: PowerMac4,2 CPU Type: PowerPC
G4 (2.1) with what I thought was a 40 MB Hard Drive.

I am operating OS X 10.4.6. At one time I had a TechTool Pro eDrive
installed but have since removed it using their removal tool.

If I use Disk Utility or About this Mac, I am told that the Drive
Capacity is 38.0 GB Available Space is 11.5 GB and that 21.6 GB is
used. Available plus Used adds up to 33.1 GB NOT the stated capacity of
38.0 GB.

Doing a Get Info on the Hard drive reports tha capacity as 33 GB with
Available Space is 11.5 GB and that 21.6 GB is used.

Can anyone explain the discrepancy? How much space do I really have? If
I have really "lost" 5 GB of drive space, how do I get it back?

Disk Utility reporst a single partition on the Maxtor 4D040H2 Hard
Drive of 38.03 GB.
From: Steve Hix on 9 Apr 2006 14:28
In article <090420061144290354%mason(a)jar.com>, rasberry <mason(a)jar.com>
wrote:

> I have a 15" iMac, Machine Model: PowerMac4,2 CPU Type: PowerPC
> G4 (2.1) with what I thought was a 40 MB Hard Drive.
>
> I am operating OS X 10.4.6. At one time I had a TechTool Pro eDrive
> installed but have since removed it using their removal tool.
>
> If I use Disk Utility or About this Mac, I am told that the Drive
> Capacity is 38.0 GB Available Space is 11.5 GB and that 21.6 GB is
> used. Available plus Used adds up to 33.1 GB NOT the stated capacity of
> 38.0 GB.
>
> Doing a Get Info on the Hard drive reports tha capacity as 33 GB with
> Available Space is 11.5 GB and that 21.6 GB is used.
>
> Can anyone explain the discrepancy? How much space do I really have? If
> I have really "lost" 5 GB of drive space, how do I get it back?
>
> Disk Utility reporst a single partition on the Maxtor 4D040H2 Hard
> Drive of 38.03 GB.

Some of the discrepancy is due to measuring the total byte capacity of
the drive, and figuring (or not) the amount lost by formatting
information on it.

Mostly it's due to measuring the capacity in Gigabytes in terms of base
2 or base 10:

A billion in base 2 is 2^30; 1,073,741,824

A billion in base 10 is 10^9; 1,000,000,000.

Blame marketing, since they use whatever looks bigger; nobody will
defend them.
From: Tom Stiller on 9 Apr 2006 14:32
In article <090420061144290354%mason(a)jar.com>, rasberry <mason(a)jar.com>
wrote:

> I have a 15" iMac, Machine Model: PowerMac4,2 CPU Type: PowerPC
> G4 (2.1) with what I thought was a 40 MB Hard Drive.
>
> I am operating OS X 10.4.6. At one time I had a TechTool Pro eDrive
> installed but have since removed it using their removal tool.
>
> If I use Disk Utility or About this Mac, I am told that the Drive
> Capacity is 38.0 GB Available Space is 11.5 GB and that 21.6 GB is
> used. Available plus Used adds up to 33.1 GB NOT the stated capacity of
> 38.0 GB.
>
> Doing a Get Info on the Hard drive reports tha capacity as 33 GB with
> Available Space is 11.5 GB and that 21.6 GB is used.
>
> Can anyone explain the discrepancy? How much space do I really have? If
> I have really "lost" 5 GB of drive space, how do I get it back?

There are two issues here. One is the often discussed 1000 vs 1024
issue and the other is exactly what is meant by "used" space.

For an example of the first, open a terminal window and type the
commands:

df -k
df -m
df -g

The first will show the number of 1024 (1K ?) byte blocks,
the second will show the number 1024*1024 (1M ?) blocks, and
the third show the number of 1024*1024*1024 (1G ?) blocks.

For the second question, consider that the disk contains not only file
data, but also metadata about the drive itself (e.g. allocation vectors,
etc.) as well as filesystem structural data. If this data is tagged as
"assigned", then the sum of all file sizes will come up short. If this
data is tagged as "available", then the disk will seem to fill
prematurely.

>
> Disk Utility reporst a single partition on the Maxtor 4D040H2 Hard
> Drive of 38.03 GB.

--
Tom Stiller

PGP fingerprint = 5108 DDB2 9761 EDE5 E7E3
7BDA 71ED 6496 99C0 C7CF
From: 42 on 9 Apr 2006 15:35
In article <090420061144290354%mason(a)jar.com>, mason(a)jar.com says...
> I have a 15" iMac, Machine Model: PowerMac4,2 CPU Type: PowerPC
> G4 (2.1) with what I thought was a 40 MB Hard Drive.
>
> I am operating OS X 10.4.6. At one time I had a TechTool Pro eDrive
> installed but have since removed it using their removal tool.
>
> If I use Disk Utility or About this Mac, I am told that the Drive
> Capacity is 38.0 GB Available Space is 11.5 GB and that 21.6 GB is
> used. Available plus Used adds up to 33.1 GB NOT the stated capacity of
> 38.0 GB.
>
> Doing a Get Info on the Hard drive reports tha capacity as 33 GB with
> Available Space is 11.5 GB and that 21.6 GB is used.
>
> Can anyone explain the discrepancy? How much space do I really have? If
> I have really "lost" 5 GB of drive space, how do I get it back?
>
> Disk Utility reporst a single partition on the Maxtor 4D040H2 Hard
> Drive of 38.03 GB.
>

There are several places lost space goes:

1)

Every first year computer science student knows that a kilobyte is 1024
bytes (2^10 bytes). However, kilo-unit, in the SI/metic unit system is
1000 units.

This discrepency plays out in the real world...

Manufacturers choose to define a GB using the SI/metic system, as 1
billion bytes:

10^9 = 1,000,000,000 bytes = 1GB

Computer science and software, thinking in binary, define a GB as:

1024^3 or equivalently 2^30 = 1,073,741,824 bytes = 1GB

This difference leads to the 40GB to 38GB discrepency you see.

Manufacturers count in base 10 (primarily because the number is a bit
bigger so its better marketing), while software/operating systems use
the binary based units.

Some software just reduces everything to actual bytes to eliminate
confusion: so while we could legitimately call it 40GB or 38GB. If we
just print out the actual byte count 38 x 1,073,741,824 bytes =
40,802,189,312 bytes.

----

2) The filesystem itself uses space, to describe and document where
everything on the disk is. This uses quite a bit of space. Operating
systems don't usually count this space, as "used".

Thus a 40,000,000,000 byte disc is really 38GB, and after you partition
and format the blank 38GB disc with a filesystem, there might only be
33GB of available space for files.

-cheers,
From: David Empson on 10 Apr 2006 04:50
rasberry <mason(a)jar.com> wrote:

> I have a 15" iMac, Machine Model: PowerMac4,2 CPU Type: PowerPC
> G4 (2.1) with what I thought was a 40 MB Hard Drive.
>
> I am operating OS X 10.4.6. At one time I had a TechTool Pro eDrive
> installed but have since removed it using their removal tool.
>
> If I use Disk Utility or About this Mac, I am told that the Drive
> Capacity is 38.0 GB Available Space is 11.5 GB and that 21.6 GB is
> used. Available plus Used adds up to 33.1 GB NOT the stated capacity of
> 38.0 GB.

Something weird is going on.

On my PBG4 (also running 10.4.6, single partition) a Finder Get Info and
Disk Utility on the volume report numbers which agree within 0.01 GB:
used (50.33) + available (5.55) = capacity (55.88).

In Terminal, if I use the "df -g" command, it shows identical figures
(to 1 GB resolution) and "df -m" agrees to 1 MB resolution.

System Profiler doesn't show a "used" figure but its "available" and
"capacity" figures agree with the other two (5.55 and 55.89). It also
shows the capacity of the entire drive as 55.89, so the partition table
overhead is too small to register. Disk Utility agrees with System
Profiler as to the drive capacity if I click on the icon for the drive
rather than the icon for the volume.

> Doing a Get Info on the Hard drive reports tha capacity as 33 GB with
> Available Space is 11.5 GB and that 21.6 GB is used.

It sounds like you have an extra 5 GB partition somewhere.

> Can anyone explain the discrepancy? How much space do I really have? If
> I have really "lost" 5 GB of drive space, how do I get it back?
>
> Disk Utility reporst a single partition on the Maxtor 4D040H2 Hard
> Drive of 38.03 GB.

Disk Utility might be lying, if you have clicked on the "Partition" tab.
It shows the partition scheme it is proposing should you wish to
repartition the drive, which might not exactly match the current
partition scheme.

System Profiler should show figures for the capacity of the entire drive
and the capacity of the volume on the drive (as does Disk Utility if you
click on the drive icon and the volume icon). If these figures don't
match, then you either have a hidden partition or some free space which
isn't allocated to a usable partition.

To be absolutely certain, you can use the 'pdisk' command in Terminal to
examine the partition map directly. This has to be run as the root user
via 'sudo' and be extremely careful what you type, because it can change
or wipe your partition table if you give it the wrong options.

As an administrative user, type the following command (better still,
copy and paste it).

sudo pdisk --list

(You will be asked to enter your password, which is the normal one for
your administrator account on the computer.)

It should display something resembling this (output for my drive):

Partition map (with 512 byte blocks) on '/dev/rdisk0'
#: type name length base ( size )
1: Apple_partition_map Apple 63 @ 1
2: Apple_Driver43*Macintosh 56 @ 64
3: Apple_Driver43*Macintosh 56 @ 120
4: Apple_Driver_ATA*Macintosh 56 @ 176
5: Apple_Driver_ATA*Macintosh 56 @ 232
6: Apple_FWDriver Macintosh 512 @ 288
7: Apple_Driver_IOKit Macintosh 512 @ 800
8: Apple_Patches Patch Partition 512 @ 1312
9: Apple_HFS T2 117208408 @ 1824 ( 55.9G)
10: Apple_Free 8 @ 117210232

Device block size=512, Number of Blocks=117210240 (55.9G)
DeviceType=0x0, DeviceId=0x0
Drivers-
1: 23 @ 64, type=0x1
2: 36 @ 120, type=0xffff
3: 21 @ 176, type=0x701
4: 34 @ 232, type=0xf8ff

In my case, partition number 9 is the actual volume (originally named
"T2" when I set up the drive). As you can see it shows a capacity of
55.9G, and the total of all the other partitions is less than 2048
blocks (1 MB), so the difference doesn't even register in the total
capacity when measured in GB to one decimal place.

The 10th partition is a small amount of free space: 8 blocks or 4 KB
total; presumably Disk Utility always leaves a tiny bit of free space at
the end.

I suspect you will see your main "Apple_HFS" partition to be about 33 GB
and you will have about 5 GB in the "Apple_Free" partition, or there
will be an additional 5 GB partition which isn't able to be mounted.
This is likely to be a leftover effect of the TechTool Pro eDrive.

Assuming I'm right, the only way to recover this space is to repartition
the drive. Doing this with Disk Utility will wipe the drive, so you
should do something like clone the drive to an external one, confirm
that you have a good copy (and it is bootable), then repartition, then
clone everything back again.

There are some third party tools which can dynamically resize a
partition (especially when increasing the size of a partition into
adjacent free space), but I'd recommend doing a full backup anyway
before attempting something like this.
--
David Empson
dempson(a)actrix.gen.nz
 | 
Pages: 1
Prev: iTunes for all users?
Next: Who's connected to my computer?