[Simh] Disk info request

[Johnny Billquist]

On 2016-03-09 16:50, hb wrote:
> On 03/09/2016 09:53 AM, Johnny Billquist wrote:
>> Do VMS and ODS-2 really try to figure out a geometry per disk for MSCP
>> disks???
>
> The ODS2 utility needs to "mount" the disk. I know nothing, but ODS-2 on
> VMS probably only cares about LBNs and VBNs (and on on-disk data
> structures). It is the mount utility which knows or needs to know the
> geometry, to do the geometry based search for alternate home blocks
> (there is also a non-geometry based search algorithm). And the mount
> utility probably uses the same code as the init utility, which writes
> the alternate home blocks. And both probably request the information
> from some other (driver) code level.

Right. But I would have assumed that VMS would just create some fake 
concept of what the geometry is for an MSCP disk, since it don't really 
make sense to try and figure out the geometry in the first place. Or at 
least that is my understanding.

There is no guarantee that there even is any "sane" geometry.

	Johnny