PDP-11 disk image question

[Glen Slick]

On Wed, Feb 20, 2019 at 8:57 AM Charles Anthony via cctalk
<cctalk at classiccmp.org> wrote:
>
> However, in the original posters case, the SIMH disk image is being copied
> to the RA81 drive without the benefit of the MSCP controller (if I
> understand correctly). This would lead to track misalignment and could
> result in the observed behavior.

How could you possibly write to a real RA81 drive without going
through a real KDA50 or UDA50 MSCP controller? Nothing like that is
happening in the original post. Just the disk size was chosen to be
that of an RA81, and the issue is to exactly match the emulated disk
size to that configured by the hardware, which is an MSCP SCSI
controller and drive in this case.