Formatting disk to add as additional storage

[Szilveszter Ciurdar]

Greetings.

I have a UNIX server which dual boots GNU/Linux and OpenBSD.  The two OS
are on the same physical disk.  Puffy is getting hungry and I want to
format and add another drive to use as additional storage.  I usually
create my partitions and slices when installing the OS, so I'm not
familiar with the commands to do this from the command line.  Thanks.