Q: I am thinking about upgrading to a flash based iPod (like the iPod touch), and I am wondering if the real storage capacity is closer to the 8, 16 or 32 GB claimed. My 5G 30GB iPod only has an actual storage capacity of 27.84GB after software.
A: In reality, the listed versus actual storage capacities for all iPod models have very little to do with installed software and more to do with differences in how storage units are calculated and advertised by hardware vendors versus how they are reported by software.
To a hardware manufacturer, one Gigabyte is equal to 1,000,000,000 bytes, whereas software being binary in nature uses a base-2 system where one Gigabyte is actually 1,073,741,824 bytes.
This is the main reason your computer only reports a storage capacity of 27.84GB for your 30GB iPod. Your 30GB iPod has a capacity of 30,000,000,000 bytes, which divided by 1,073,741,824 equals approximately 27.93. The remaining small difference (0.09 GB or about 90 MB) is attributable to the iPod operating system and software files itself.
Note that this is no different from your computer hard drive. A 160GB hard drive in your computer will only have a “real” capacity of around 149GB as far as your computer’s operating system software is concerned.
This does not change with flash memory chips. A 32 GB iPod touch is going to have a capacity of 32,000,000,000 bytes, which your computer will report as approximately 29.8 GB. The iPod touch operating system and support files are actually larger than the traditional iPod models due and will take up about another 300 MB, leaving you with around 29.5 GB of actual usable space as far as your computer is concerned.