Dumb question - New Mac Pro and HD

[denald]

I just got me new Mac Pro and yesterday installed a 750GB HD to go with the 320GB that came from Apple. I know each drive has system files to operate the drive after you format it but why does a 750GB only have 698.1 GB available? Does it take 50 GB for this data?

I am sure there is a logical reason but 50GB?

Thanks to anyone who can explain this to me.

Denny

 

[robbieduncan]

There are no "system files" on the second drive. There is a very small overhead for formatting the drive, but not much.

What you are seeing is the well known, common issue that the OS reports drive size one way and drive manufacturers the other. This has been the case ever since hard drives have existed and is the same in all OSes.

Basically the OS thinks a kb is 1024 bytes, but the drive manufacturer 1000 bytes. This continues all the way up (the OS thinks 1 megabyte is 1024 kilobytes, the drive manufacturers 1000). This all adds up to a very significant loss, which I'd not be surprised if it was around 50Gb on a 750Gb drive once the format overheads are all taken into account.

The "250Gb" drive in my laptop is only 232.57 when formatted. Your drive is 3 times larger, as is your "loss".

 

[snagitseven]

I just got me new Mac Pro and yesterday installed a 750GB HD to go with the 320GB that came from Apple. I know each drive has system files to operate the drive after you format it but why does a 750GB only have 698.1 GB available? Does it take 50 GB for this data?

I am sure there is a logical reason but 50GB?

Thanks to anyone who can explain this to me.

Denny

It's not the system files that use that space but it's the formatting that sucks it up. This is true for all drives on any computer. Also, I believe there's a difference between what the manf states and the actual capacity. I've seen this on all my drives over the years. The larger they are, the more is used.

 

[snagitseven]

There are no "system files" on the second drive. There is a very small overhead for formatting the drive, but not much.

What you are seeing is the well known, common issue that the OS reports drive size one way and drive manufacturers the other. This has been the case ever since hard drives have existed and is the same in all OSes.

Basically the OS thinks a kb is 1024 bytes, but the drive manufacturer 1000 bytes. This continues all the way up (the OS thinks 1 megabyte is 1024 kilobytes, the drive manufacturers 1000). This all adds up to a very significant loss, which I'd not be surprised if it was around 50Gb on a 750Gb drive once the format overheads are all taken into account.

The "250Gb" drive in my laptop is only 232.57 when formatted. Your drive is 3 times larger, as is your "loss".

You are absolutely correct. I misstated that the stated capacity is different than the actual capacity but meant to write that it's the Mac way of counting bytes that's the difference.

 

[Brianna]

You are absolutely correct. I misstated that the stated capacity is different than the actual capacity but meant to write that it's the Mac way of counting bytes that's the difference.

That has always totally pissed (pardon my french) me off about drive manufacturers. Everyone knows a megabyte is 1024 kilobytes, and a kilobyte is 1024 bytes and so on. What 1000 is close enough?

 

[denald]

Thanks

I knew you could explain it and that makes sense. Is the drive half empty? Is the drive half full? Well, at least I have a new Mac Pro.

thanks

Denny

 

[amik]

That has always totally pissed (pardon my french) me off about drive manufacturers. Everyone knows a megabyte is 1024 kilobytes, and a kilobyte is 1024 bytes and so on. What 1000 is close enough?

Because SI prefixes like kilo, mega, giga all originated as base 10. Using them to describe base-2 numbers is wrong.

IEC has listed binary prefixes and the BIPM has actually stated that they prohibit the use of SI prefixes for use in binary systems (http://physics.nist.gov/cuu/Units/binary.html). The IEC binary prefixes are kibi, mebi, gibi, tebi, and so on. http://www.iec.ch/zone/si/si_bytes.htm

Since all drive manufacturers use the same conventions, what is the difference? When you compare two 1TB drives they are going to have the same actual capacity as one another, so any $/gb comparisons will still be valid on a relative percentage basis. I can see a problem if only some manufacturers switched to Base-2 stated capacities, because they would appear to have more expensive drives than competitors reporting in base-10. It needs to be a federally (probably internationally) mandated switch if it is going to work.

 

[Lord Zedd]

The 50GB is used by the government to store records of your activities.