How to understand partition sizes

[Olivier Nicole]

> The /server is 9Gb smaller than I partitioned and the actual free space 
> without any files in the partition is shown as 396.5Gb which is another 
> 34.5Gb smaller.

The number of disk sectors/blocks allocated to a partition at install
is reduced by the amount of space taken by the system to put file
system information (table of inodes, etc.) plus some percentage of
space kept for security reason (so the operating system can fill up
your partition by more than 100% in case of emergency).

Olivier