Missing disk space

[pjcurtin08]

Hello All,

I have a strange issue. I recently wiped my computer using the disk utility and did a clean install of snow leopard. Then, I realized the person I was selling the computer to wanted Leopard because of compat. issues. So, in the snow leopard disk utility (boot up from disk), I deleted the partition, and it showed I had 320GB of free space. So, I boot up to Leopard DVD, and it says I have 300GB of free space. What could the problem be here, I haven't even installed Leopard yet, but its only showing I have 300GB...

Thanks,
Patrick

 

[TEG]

320GB as the drive is labeled is 320,000,000,000 - whereas the computer will report it as less than 300x2^30 = 322,122,547,200.

TEG

 

[spinnerlys]

Snow Leopard uses the decimal system to show HDD space, so 320.000.000.000 bytes are shown as 320GB, but Leopard uses the binary system so 320.000.000.000 bytes are 298GB.

320.000.000.000 / 1024 / 1024 / 1024 = 298

2^10 = 1024

 

[MacDawg]

Check out the Guide here at MR: Hard Drive Size Discrepancy

Hard Drive Size Discrepancy

Why does my new 500 GB hard drive report it only has 465 GB? Have I been ripped off?

No, you haven't been ripped off. 500 GB = 465 GB, strange as it seems.

The reason is that computers count a "kilo" something as 1024 (binary 2^10) while the rest of the world count a "kilo" as 1000 (decimal 10^3). A 'mega' in computer binary system is 1024 x 1024 = 1,048,576 (rather than decimal 1,000,000), and a 'giga' is 1024 x 1024 x 1024 = 1,073,741,824 rather than decimal 1,000,000,000

This creates a discrepancy of approximately 7% between the number of GB the computer reports, and what is advertised as the drive's capacity in GB. It is important to note that there is no difference in the number of actual bytes of storage - it is only a difference in reporting when the binary 'giga' terminology is used.

A 500 GB hard drive has about 500,000,000,000 bytes (it is never exact, commonly a drive is designed to have more bytes, to allow for a certain number of defective sectors to be mapped out). When counted on the computer, 500 Gb (decimal) = 500 billion bytes = 465.66 GB (binary).

Some propose using a different term, gibibyte (GiB) for the binary figure, however that is unlikely to catch on in the marketplace.

 

[pjcurtin08]

Okay, so the sizes are equal. But, what will happen when I get down to low disk space. Will there be an extra 20GB available?

 

[spinnerlys]

Okay, so the sizes are equal. But, what will happen when I get down to low disk space. Will there be an extra 20GB available?

No, there will be no extra 20GB available.

When Snow Leopard (10.6) shows 100GB free, Leopard (10.5) will show 93GB free.

10.6: 20GB
10.5: 18.6GB


10.5: 20GB
10.6: 21.47GB


The actual disk space is the same, just the reporting of it differs. But the lower the free disk space the lower is the difference between the two reporting methods.

 

[cube]

300 GiB ~= 320 GB