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Used HDD Space after formatting
- Thread starter OngL
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This a very common question that comes up on MR- so an explanation was put in the Mac Guides here to avoid repeating the info over and over. What is comes down to is two different number systems- decimal for marketing purposes (makes the size seem larger) vs. binary (which is what the computer sees).
Check out the full explanation at the Mac Rumors Hard Drive Size Discrepancy guide.
Check out the full explanation at the Mac Rumors Hard Drive Size Discrepancy guide.
Point noted on search, sometimes, I couldn't get the right thread. Anyhow, I have a hunch but not confirmed that the 300+ MB is used by file system structure e.g. FAT in MS-DOS system, but this is HFS+.
It has nothing to do with 1000 vs 1024 bytes / KB..
Again, I'm not asking why I don't get 2048 GB for 2 TB harddisk, what I am asking, out 1.8TB, there is another usage of 300+ MB.
Yes, it does. Your hard drive manufacturer uses 1000, your computer uses 1024. Thus, the discrepancy.
While I appreciate your answer, but you're answering what I did not ask.
2TB HDD theoritically should be 2048 GB, however, I only get 1862.6. I am aware of this and not referring to this. I believe you're referring to this.
What I'm referring is that out of available capacity of 1862.6 GB, there are usage of 300 MB to become 1862.3 GB without any files added at all.
Did I make any sense?
Oh okay...yeah, that's the overhead from formatting your hard drive. It exists with all file systems, HFS included.
Just for confirmation: I recently formatted my 500 GB HDD into Extended/Journaled and I too have that kind of usage - it's about 150 MB. I noticed that when I selected the HDD for my TM backup, it showed this usage.
Can someone explain what "overhead from formatting" exactly means?
Its space the file system needs to keep track of the files on your hard drive. On a hard drive that big, a few hundred megabytes is no big deal.
OK- I will try again then. The 2Tb on the box is a marketing number based on decimal base 2 numbers in which a kilobyte=1000 byte. The usable space is based on binary in which a kilobyte=1024 bytes. Of course the marketing people want it to seem like more on the label, but the computer does not recognize it in the same way. There was even a lawsuit filed over the standard industry practice (here in an article from Wired Magazine) claiming "deceptive practice".
There is a calculator online to do the math for you, so go to here. Enter 1000 for the advertised hard drive size in gigabytes (since the calculator only goes up to 1.5Tb use 1000Gb since that is 1Tb). Then take that result (931.32Gb) and multiply by 2 for your 2Tb disk's usable size. 1862.64Gb.
Based on a little simple math the reverse of this fact is that to make a drive with 2Tb of usable space in binary as understood by the computer, a drive would have to have 2.147Tb of space in marketing's decimal base2 system. That probably wouldn't look too cool on a package- "Yeah, I'm headed to Best Buy to pick a new 2.147Tb drive!"
And from the FAQ that I linked to it mentions estimating size differences by using an approximately 7% difference between the marketing and usable numbers. In your case just based on that, your 2Tb drive has 1.86Tb usable.
You do realize you just posted a lengthy reply that had zero applicability to the actual question being posed, right? He wasn't asking about that, he was asking about the space being used on the drive. Not a mismatch of numbers, an actual reading of space being used. The question's been answered despite your attempts, but still, try to read a bit (it was a good explanation, btw, just not relevant).
jW
Mal- you are so right and it was my bad.
Thank you for pointing that out. The size discrepancy issue is so common, I did indeed read this one incorrectly, so will delete the previous response! Thanks for pointing that out. What's interesting is that you and I have almost identical posts counts (1700+), so I should have read it as well as you did.Mal- you are so right and it was my bad.
Heh, we all do it. Post count's don't really matter much, btw. I've seen really high post counts from some of the worst posters and some really good posts from completely newbie's. I've made plenty of mistakes myself.
jW