Incorrect capacity of backup media

[anothersmurf]

I have a brand new 750GB USB3 hard drive, with no files on it, that I want to use for backup media. Get Info confirms the amount of free space on the drive. But when I create a new media set and point to that drive, Retrospect says that 100% of the drive's capacity is 697GB. I tried to change the 697 to 740, but it changed back into 697.

 

How can I make Retrospect use the full capacity of the drive?

[prl]

I think that the problem is the two different common definitions of GB, one being 10⁹ bytes, and the other being 2³⁰ bytes (more properly GiB or gibibyte). Most likely, the HDD manufacturer is using GB, and Retrospect is using GiB, because 750 GB = 698 GiB. 1GB ~= 0.9313 GiB. OS X Get Info also uses the 10⁹ bytes definition of GB.

 

So most likely there's nothing missing and Retrospect is using all the available space.

[anothersmurf]

Thanks, that makes sense. Though the label in Retrospect's GUI is GB not GiB.

[prl]

Thanks, that makes sense. Though the label in Retrospect's GUI is GB not GiB.

Few people know about, and even fewer use, the binary prefixes (Ki, kibi- (2¹⁰ = 1024); Mi, mebi- (2²⁰ = 1024²); Gi, gibi- (2³⁰ = 1024³); Ti, tebi- (2⁴⁰ = 1024⁴); etc. It's not just Retrospect that's like this. Main memory sizes are almost always written as, say, 4 GB, when what is meant is 4 x 1024³, and where it would be clearer to use 4 GiB.

 

Unfortunately, there is also a JDEC standard where K = 1024 (rather than k for 1000), M = 1024² and G = 1024³. Just to help confuse things.