[Coco] SCSI tape driver for OS-9?

[Gene Heskett]

On Wednesday 15 July 2009, Tim Fadden wrote:
>Gene Heskett wrote:
>> On Wednesday 15 July 2009, Steven Hirsch wrote:
>>> On Wed, 15 Jul 2009, Gene Heskett wrote:
>>>> On Wednesday 15 July 2009, Steven Hirsch wrote:
>>>>> Just curious if anyone has seen a tape driver for OS-9 or any tar-like
>>>>> applications for backup?  I have a Cloud-9 SCSI cartridge and would
>>>>> love to use one of my older streaming tape drives for backup.
>>>>
>>>> It would have to be a really old slow drive, else the coco's streaming
>>>> speed would likely 'shoe-shine' the drive to death in short order.  Even
>>>> at the optimum interleave on the floppy for bru, it still took around 9
>>>> minutes to write a 765k floppy with bru.  But the killer was the 33
>>>> minutes it took to restore from that same floppy.  Multiply that by the
>>>> approximately 90 such disks it took to backup what was on the old Maxtor
>>>> 120 megger, and you can see why I only did that once.
>>>
>>> Yes, I believe you have nailed that one.  I keep forgetting how slow the
>>> throughput is on these old mu-chines :-).
>>>
>>> I probably should link in the DriveWire driver and just copy the hard
>>> disk over the wire.
>>
>> And I expect that would be faster if drivewire is setup to smoke.
>
>Took me about 6 hours for 70meg worth of data on a 105meg drive using dsave.

That is 11,666,666.6667bytes/hour or 194,444.444444 bytes/minute and 
3,240.74074074 bytes/sec.  It seems to me that drivewire ought to be faster 
when I can do a megaread in 13.5 secs on a stock coco, and in 11 secs on my 
63C09 equipt home machine.  Not counting housekeeping, which on a coco is 
considerable when its writing as opposed to reading, that means it should move 
around 5megs/minute.  I don't think rbf.mn's housekeeping can account for the 
missing 4.8 megs/minute.

OTOH, dsave isn't exactly a speed daemon either.  I dunno, so I'll shaddup. :)

One thing that will help, set the descriptors SAS (default 8) up to FF for the 
run, you'll get no fragmentation & won't waste rbf's time going back to the 
fat for 8 new sectors for every 2048 bytes written.  That change alone can 
double the speed when writing cuz most files will be written in one chunk (one 
fd.seg entry in the fd sector) and rbf gives back the unused disk when the 
file is closed.

Just my $0.02, adjust for inflation. :-)

-- 
Cheers, Gene
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