iMac not seeing full size of new harddrive
 

Just bought a new Lacie Big disc extreme + 2TB harddrive and my iMac is only seeing 1.82 TB. I know you can never access all of the space on an external drive, but 180 gigs worth? What's going on with that. Sorry if this has already been answered. Search function is apparently under maintenance right now.

It's because the manufacturers call a 2000GB drive a "2 terabyte" drive when it should really be 2048GB. It's a misleading description really.
EDIT: and their GB sizes are wrong too - they should be 1024MB

Wouldn't that mean that more than 2,000 gigs are available then? Why is less available?

1 Terabyte = 1024 Gigabytes (not the 1000 that LaCie allow)
1 Gigabyte = 1024 Megabytes (not the 1000 that LaCie allow)

So 1 Terabyte = 1,048,576 Megabytes (not the 1,000,000 that LaCie allow)

The true sizes are powers of 2 (2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2148 etc).
I think all the drive manufacturers use these short measures to describe their products. Your computer is showing the true available capacity.

The true capacity of my "250 GB" internal hard drive on this MacBook Pro is 232.89 GB. You do lose a wee bit for formatting, but most of the difference is the inaccurate description of the hard drives's capacity.

I'm sorry, maybe I'm dense, but I'm still not getting this. You seem to be saying that hard drives have a higher capacity than the manufacturer makes available. So why would I be seeing less?

I do see that you say some is lost to formatting. I was aware of that, but it seems like an awful lot. Do you really lose 10 percent to formatting? Maybe it seems like so much because the drive is so big to begin with. Sheesh, 200 gigs is bigger than the internal hard-drive on my old G4.

OK, think of it this way:
A hard drive that has a 1000MB capacity is not 1 gigabyte, it's only 0.9765625GB because a gigabyte is 1024MB, not 1000MB. LaCie and others call 1000MB "gigabyte" but it's not - it's a misleading description that they seem to be allowed to get away with.

They do the same with terabytes. Your drive is called "2 terabytes" but it's not really, it's only
2000MB (and remember the "megabytes" are misleading) instead of the 2048MB it should be.

So your drive capacity is smaller than you were lead to believe when you bought it. Simple really, but I don't know why this is allowed. There will be a disclaimer somewhere in the documentation.

EDIT: This may help http://www.popularmechanics.com/how_...y/4206535.html

Actually you lose 7%. You are already short from the factory due to the reason Colin explained. In other words it looks like this:

2 Terabytes = 2048GB in terminology
2 Terabytes = 2000GB in manufacturing specs

Then take 7% away from that, and you have your 1.82TB

Yep, that's exactly what it is. Think of it as you owning 1% of a 14billion dollar company ; ).

JS

Ah, thanks Colin! That makes sense now. :)

There were actually some lawsuits related to this issue recently. In the end, it's really about semantics and not actual storage capacity. See: FOXNews.com - Western Digital Settles Hard-Drive Capacity Lawsuit - Science News | Science & Technology | Technology News

A hard drive stores bytes linearly, and so a terabyte is measured as 1 trillion bytes (just as a terawatt is 1 trillion watts). Your 2TB hard disk holds 2,000,000,000,000 bytes. So, it is unfair to say the manufacturer is being "deceptive" about the disk capacity. After all, if you bought a kilogram of sugar and received 1000 grams, you wouldn't complain that you were missing 24 grams, right?

The problem is that computer memory is always arranged in blocks which are the size of a power of 2. For convenience sake, early PC programmers referred to 1024 (2^10) bytes as a "kilobyte" even though all other scientific uses of kilo mean 1000 (i.e. a kilometer is 1000m not 1024m, and a megawatt is a 1000000 watts not 1048576 watts). The difference for a kilobyte is only 24 bytes and even in those days it was considered to be a negligible difference.

Since early computers had at most a few kilobytes of memory and the idea of a gigabyte or terabyte was absolutely unimaginable, this discrepancy was not so important. However, each time you increase an order of magnitude, the discrepancy gets bigger both in number of bytes and as a percentage of actual size.

Since your operating system deals with files that need to be moved in and out of memory and are processed in binary, it uses the memory definition (kilo=1024) instead of the true standard definition (kilo=1000). Thus by your OS's definition, a terabyte is 1,099,511,627,776 bytes. When counted this way, your 2,000,000,000,000 byte drive only holds 1.82TB or 1,862GB.

Kilo: 2^10/10^3 = 2.4% difference
Mega: 2^20/10^6 = 4.8% difference
Giga: 2^30/10^9 = 7.4% difference
Tera: 2^40/10^12 = 10% difference
Peta: 2^50/10^15 = 12.6% difference
etc.

I guess a few years from now, we will have people asking why their shiny new 1PB (1000TB) hard drive only holds 909TB. =)

Mmmmmmm.... a Petabyte drive... <wipes drool from face>

But by then, we'll all be shooting 4k footage at 200 fps uncompressed so we'll STILL only get a dozen hours or so on a drive...

PS. Oh, and the footage will be stereo with a built in alpha channel and 3d information.

i hope my spaceship will have an 8-track or a phonograph.
i thought a Petabyte was a dinosaur or a Star Trek alien...