GEOM meaning

[Frank Leonhardt]

On 04/02/2014 10:46, Dieter Lange wrote:
> Hi,
>
> having looked at quite a few sites now, not just 
> <http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/geom.html> 
> I still cannot find out what "GEOM" means (wrt disks etc., not 
> geography or so).  It probably does not mean "Modular Disk 
> Transformation Framework". I am not talking of its use and/or 
> definitions, just the meaning of the abbreviation or word...
>
> Thanks+kind regards from the only person on the WWW who doesn't know...
> DL

I've always assumed it was short for (disk) geometry - i.e. converting 
logical requests to match the disk geometry. Eh? Well, back in my youth 
we did talk about the "geometr"y of DASD (disk!). For example, how many 
platters (heads), cylinders (tracks) and sectors/track were present. 
With ATA and SCSI this has become less relevant as you only get to see 
the logical structure of a disk (a load of blocks sequentially numbered 
0...n). You may well ask why anyone would call these parameters 
"geometry", but I can't think of any other better name for it, nor any 
other word in common use for referring to them (other than CHT). But a 
disk's geometry was highly relevant because you (the programmer) would 
either be responsible for moving the head (via a stepper motor) to the 
correct track, or at the very least, you had to be sensitive to where 
the head was on the disk when optimising your code.

I've no proof whatsoever that this is why the geom library is so called 
- it could all be a complete coincidence. I don't remember hearing about 
"geom" on System V, nor on BSD until recently (late 1990s).

Regards, Frank.