< Connecting Fujitsu M2266SA to SGI SCSI (SOLVED) >

[Tom Glinos]

I too bought a 2266 in the hopes of connecting a BIG, FAST, and CHEAP
drive to what is a relatively fast machine (4D220).

The drive came configured from our vendor and it almost worked.
A lot of hours later I had a drive that ran. But it ran SLOWWW.
Top speed of about 900KB/sec. Way short of the rated 5MB/sec.

Inspection of DKS(7M), Kernel Specifications (Tuning and Config Guide),
and examination of the dksc.c (kernel scsi driver) all lead to you believe 
that you can run this drive in synch mode. The documentation states
that you can get 1.25-2.5MB/sec (raw) through their SCSI adapter.

Experimentation showed that running in synch mode was impossible.
SGI had the following to say (heavily edited):

	"It's not really documented in the manuals-Sorry 
	It might be in Marketing & Eng Spec sheets.
	.
	.
	.
	Synchronous SCSI is never enabled on IO2 or IP4 machines, because
	there would be no performance benefit.  SCSI transfer rate is
	limited by how fast data can be pushed from the 3393 into memory,
	and not by how fast it can be pulled off the SCSI bus.  Therefore,
	it was decided not to enable this feature, since the only thing
	it could do would be to cause problems."

Yes, I too am sorry. Let's get with it SGI. Your manuals are incorrect.
Let's get them fixed! (To be fair the cryptic remark in DKS should have
set off warning bells)

Still not satisfied I'm trying to get the very last drop of performance
out of the drive. Why won't it run any faster than 900KB? The drive is
rate for 2MB/sec in asynch mode. 

A call to Fujitsu indicated that 
	"in my configuration 1MB/sec was a good number." 

The nuance of the phone call was that unless you had some VERY good
SCSI equipement your aren't going to get anything near 2MB/sec.

In addition there are all sorts of problems when trying to boot with
our 3rd party exabyte on the bus as well.

The moral of the story is that if you are planning your future storage
needs and want to go SCSI then plan on buying a POWERCHANNEL 
(known as an IO3) or another 3rd party SCSI controller.

=======================================================================
tom glinos		| "I do not know of a crime man can not commit"
tg at utstat.toronto.edu	|      some 13th century philosopher