There's also the overhead of the JFS filesystem.  When you create with 
"Large File" also don't use defaults, use "Number of Bytes per inode" of 
at least  32768 and this will give you a few more hundred MB of space.  
After FS is created, use df -k to see what you actually have available and use 
that.

(Remember the MB vs million bytes!!)

David Longo

>>> jrmartin AT KNS DOT COM 11/21/01 10:51AM >>>
In the Admin Reference for v3.7 it says...

the allocated file size is always a multiple of 4MB plus an additional 1MB
ofr overhead).

Don't know how much that will help answer your question.

Thanks,
Jon