Question From The Crowd: Hard Drive Space

In the last week I’ve had this conversation come up two times, so I thought it must be worth a blog post to discuss. The question revolves around why, when you buy a product that advertises N GB of disk space, do you never get that N amount of space?

The answer is that there are a few factors. The first is that the storage industry and the software makers differ on what a GB(gigabyte) is. A gigabyte is defined as 1000 MB(megabytes) for hard drives, but in reality it’s 1024 MB. Why is this? Well 1000 is easy for people to understand, where 1024 is more confusing, if more precise. If you look on boxes for hard drives, it always lists in small lettering that they define a gig to be 1000 MB. They also define a MB to be 1000 KB(kilobytes), when again it’s 1024. In this manner, they are able to skimp you on a bunch of extra space they’d rather not add in, while still being able to advertise it as N GB.

So our first problem is a marketing one, because of the 1000/1024 difference (you get 1024 if you use the binary system, and double your amounts starting at one, so 1, 2, 4, 8, 16, etc. This is why two 512MB  sticks of RAM is 1GB). The next issue is the file system. The file system is a system put on the hard drive that tells your operating system how to understand all the little 1’s and 0’s on your hard drive and be able to find files and folders. This mapping system takes up some space, and the more spacious the hard drive, the more space the file system is going to need in order to keep track of all the bits and pieces. Also more “complex” file systems will need more space, such as if it supports directories or journaling or other nifty features.

Lastly, and this depends, is your operating system. If you have an operating system installed on a hard drive, that eats up space you could use for something else. It can be several gigs in the newer operating systems. On mobile devices you won’t have to worry about this, since they store the operating system in a special area.