where is my remaining space ????

[Alan Cox]

> First, most (all?) hard drive manufacturers define 1gb as 1000mb.  In
> reality, 1gb is 1024mb.  Therefore, a hard drive that is sold as a 320gb

In fact they are giving you more than you asked for. Giga is a prefix for
10^x series. So really they should be giving you 1000000000 bytes

> hard drive has only 312.5gb of actual space.  Calling it a 320gb hard
> drive is a marketing ploy to make it sound larger.

Its correct (slightly over) but it does confuse because computing people
used the wrong units for so long and often still do.

> You also lose some of the hard drive capacity to what you might call
> overhead; tracking and format information that allows your computer to
> store and find stuff on the hard drive.

Plus about 5% is usually reserved space for the superuser. That makes
some sense on the root partition and systems parts of the disk - although
today 5% is perhaps excessive. For other partitions its less sensible.
You can tune the reserved size with tune2fs -m

Alan