New 120Gb drive shows only 111.75 available
I installed my new Seagate ST3120024A (120Gb) hard drive this weekend. I used Drive Setup to initialize the disk. I used the HFS+ format and did not partition the drive. It seems to run fine and is so quiet that I don't know it's there. However, it shows that there's only about 111.75 Gb available. Nowhere near the 120Gb it's supposed to be. Seagate tech told me it has to do with how different manufacturers calculate disc size. Apparently, some use the number 1000 for the number of Mb in a Gb. And others use 1048. And I'd guess that 1024 would also be used for calculating Gb's. So Seagate says that I really do have 120 Gb available even though my Mac says 111.75 or so. Who's right? Seagate or my Mac? (My old Quantum Fireball KX 20Gb shows a capacity of 20 Gb or so.)
Comments
Sorry.
"GB" could mean either, which leads to most of the confusion...
Drive manufacturers all pretty much "lie" by giving the unformatted size. Once you format, partition, and the disk map is written, you lose space. The larger the drive, the more you lose. Don't worry...it's normal.
-- Ensoniq
117,187,500 Kilobytes / 1024 = 114,440.9 Megabytes
114,440.9 Megabytes / 1024 = 111.7587 Gigabytes
So, you have a drive that is 120 billion bytes in size. But 120 billion bytes, because of the 1024 bytes per kilobyte, 1024 kilobytes per megabyte, 1024 megabytes per gigabyte conversion ratios, is not equal to 120 gigabytes. It is equal to exactly 111.7587 gigabytes. Those numbers up there are all equal.
Some drives have a little extra "padding" to put them closer to their advertised capacity, but I've only rarely seen one that is exactly the same. For example, my iBook has an advertised 30 GB hard drive, but it's actually 31,000,000,000 bytes or 28.871 gigabytes. It would have been 27.93968 gigabytes had it been exactly 30,000,000,000 bytes.
Anyway, just remember the conversion ratios. 1024 bytes per kilobyte, 1024 kilobytes per megabyte, and 1024 megabytes per gigabyte. I don't think anyone here is working with terabytes but they are the same as far as I know.
Originally posted by AirSluf
A completely fabricated (not by members here) term to sow more confusion when doing numeric base conversions.
Manufacturers give capacity (usually) in base-10 numbers. Chalk most of the size difference up to the Base-10 to binary conversion. Also, a little space is lost on formatting when a few emergency blocks are set aside in each track as insurance against bad blocks appearing in use. The bigger the capacity, the bigger the difference, although the percentages are relatively constant.
If by fabricated you mean an official ISO binary prefix, then yes. It's no more 'fabricated' than the metric/SI prefixes we use today. It's just much less pervasive and practical in a decimal world.
Originally posted by WMB
What's the difference between Giga and Giba? For that matter, what the heck is Giba? That's a new one on me. Thanks.
Just the binary version of the Giga prefix so rather than being 10^9 it is 2^30.
Basically to get it you take the SI prefix remove the last 2 letters and add bi (for binary) so it goes:
10^3 = kilo = k
2^10 = kibi = Ki or K
10^6 = Mega = M
2^20 = Mebi = Mi
10^9 = Giga = G
2^30 = Gibi = Gi
and so on and so forth.
%error increases by roughly 2.4% per level of prefix if you're wondering.
Just google Gibi Giga and you'll find more on this. I really do wish OS producers would drag their feet a little less on this but I appreciate why they do.
Originally posted by Telomar
%error increases by roughly 2.4% per level of prefix if you're wondering.
Actually, it increases exactly 2.4% per level of prefix because 2^10 is 2.4% bigger than 10^3.