Common installation errors?

[Eric Dynamic]

I'm trying to install 10.3 amd64.
When I get to the "allocate disk space" and say "auto (guided)" using a 
Seagate 250 GB disk that
was previously used for Ubuntu, each choice GPT, BSD, MBR fails with the 
same error message
something like "bad geom: ada0".
Either a different disk will work, or I need to step back to 10.1, so I 
try a Seagate 80 GB disk (also
with an Ubuntu system using the whole disk) and this time despite some 
complaint that flies by,
the disk space allocation works and I can proceed with the install.

I cannot find any reference to "bad geom: <device name>" in a few 
cursory searches, but the place
to discuss such an error message is in the installation manual, which is 
currently written mostly
as if most steps will not go wrong. Surely whatever complaint the system 
had about "bad geom"
was something trivial, or hopefully correctable, since presumably BSD 
supports 250 GB .. 3 or 5 TB
disks by now; 10.1 supported install on a 1 TB drive.

May I suggest adding documentation for such common "gotchas" to the 
installation manual? Then
the installation manual is a one-stop shop.

Meanwhile, if anyone can tell me what "bad geom: ada0" meant, I'd 
appreciate it, thanks.

-ecsd (Eric Dynamic)
Berkeley