Date   : Thu, 05 Feb 2009 12:13:08 +0000
From   : philb@... (Phil Blundell)
Subject: MDFS / Nexus filesystems

On Wed, 2009-02-04 at 18:19 +0000, Mike Tomlinson wrote:
> In article <1232875950.4890.102.camel@...>, Phil
> Blundell <philb@...> writes
> 
> >Nexus was just a shared disk server, not a fileserver as such.
> >Partitioning aside, the actual filesystem layout was standard FileCore
> >-- i.e. the same as ADFS of the same vintage.
> 
> Are you sure?  The hardware of Nexus was very different to any Acorn kit
> (it used a Transputer processor) and I thought the Nexus OS was custom-
> written by SJ.

Yes, the Nexus OS was indeed custom.  But from what I remember, the OS
on the fileserver was not responsible for the filesystem layout on disk,
except for carving the space up into the right number of partitions and
managing its own boot area.  The Nexus server just presented itself to
the clients as a hard disk, or a pair of hard disks, and it was up to
them to lay out the filesystem however they wanted.  (That is, the
transactions between the client and the server were at the level of
"read/write sector N", not "open this file".)

The NexusFS implementation on the client, in common with virtually all
hard disk systems for RISC OS, delegated the filesystem management to
FileCore and hence the layout on disk would almost certainly have been
what FileCore used.

p.