Acorn Econet Fileserver

[Jules Richardson]

Tony Duell wrote:
>>> The E20 hard disk unit contains the standard Host Adapter card linked
>> to
>>> a 20NByte SCSI hard disk. That was the normal thing to link to the 34
>> pin
>>> connector on the E01. It sohuld be relatively easy to put one of
>> those
>>> together... Is there any restriction on the hard disk size? What
>> would
>>> happen if I linked up a unit of several hundred Mbyte capacity? Would
>> it
>>> just not work, would it only see it as a 20Mhyte unit, or would it
>> see
>>> the whole thing?
>> There will be some limit, but I'm not sure what it is.  More than 20MB,
>> for sure.  Might be 500MB, maybe less.  I know that stacking filestores
>> use the same code, and I know that although the largest ones sold and
>> supported by Acorn were 60MB, they had bigger in-house.
> 
> Julese Richardson seems to think there'll be a problem with the fact that 
> the Filestore will want a deive that suports 256 byte sectors.

Of course with ST506/412 you're probably OK - the Adaptec board probably 
supports various sector sizes (and of course the drive is non-intelligent and 
won't care). The only manual I have to hand is for the OMTI board, but that 
certainly supports 128/256/512/1024 bytes/sector.

But with SCSI straight to the host adapter it'll be somewhat different and the 
drive needs to support whatever the initiator requests, which I expect is 256 
bytes/sector. Acorn *might* have moved things along by then and be doing 512 
bytes/sector - although in all fairness 256 is likely more suitable for the 
nature of the data stored on a typical fileserver.

Pete, were there two releases of the format utility - one for ST-type disks 
and one for SCSI? Strictly speaking in SCSI-world there's no need to define 
drive geometry as it can be queried from the target drive itself, but this 
would be a necessary step when using an ST-type drive. (of course ST-type 
drives also need geometry subsequently stored - presumably in block 0 - which 
isn't necessary for SCSI)

Certainly prior to formatting an ST-type disk with the OMTI board you need to 
issue an 0xC2 "assign disk parameters" command to tell the board what it's 
connected to; I can't imagine this is different with the Adaptec (unless it 
does it via a vendor unique extension instead). I *think* this would all be 
unnecessary for SCSI, although I suppose it might be possible to assign 
different geometry to the SCSI drive that its physical geometry (providing you 
don't exceed total space available) and the drive would translate accordingly.

Following that it's just a case of issuing a 'format unit' command (and 
subsequent verification) to either the Adaptec board or in the case of SCSI 
direct to the drive.

So there are a lot of similarities in the process, but there's an extra step 
for ST-type drives that isn't (strictly?) necessary for SCSI.

>> making a teledisk image; that *might* work.  They're double-density,
>> 256 bytes/sector, 16 sectors/track.
> 
> Should be possible, but not a lot of use to me as I don;t haev Teledisk 
> (and don't intend to try to write soemthing to handle its images). I 
> might have a go at writing programs to handle Imagedisk stuff though.

True, Imagedisk is probably a more viable format these days (hat off to Dave 
D). I've just gained another PC, so time to see if that one supports FM 
recording on the disk interface (if not it goes in the bin - I don't need more 
hardware around here :)

>> Ditto!  The test box pre-dates the Master series, though.  It was
>> around when Beebs were.
> 
> It's a pitty the software seems to be long-lost....

I'm sure It'll turn up sometime. I don't know what it is about Acorn, but 
their stuff seems to vanish for years and then suddenly appear again. I bet 
it's lurking in someone's garage somewhere...

>>> The chap who sold this to me included a couple of such Sony
>>> drives, alas missing the front panels and eject buttons. 

I'm sure I can rustle up a pair of suitable drives through the museum if you 
have no luck (I've been deliberately rescuing 5.25" drives from landfill, but 
it's probably time to start doing the same with 3.5"...)

cheers

Jules