Adaptec 2940UW with Fujitsu MAN3184M

[Baurzhan Ismagulov]

Hello Marc,

Thanks for the prompt answer! Let's see what we can find out.

On Wed, Feb 28, 2007 at 02:31:15PM -0800, Marc D. Brooks wrote:
> The Adaptec 2940UW is Single Ended. With Single Ended, there are a 
> number of things to consider when trying to go Ultra. It is possible 
> that even though the 2940UW initially negotiates for Ultra, the domain 
> validation forces it to the slower rate due to issues seen with the 
> communications.

Any way to see those at the Linux administrator level?


> The other thing to check is if the 2940UW BIOS has been forced to the
> slower rate.

The card is branded Siemens-Nixdorf, I don't see the usual Ctrl-A
prompt. I've seen older SNI controllers, all settings were accessible
from the main BIOS. So, I guess I can't check this.

That said, when the driver is loaded, it states the USER setting of 40
MB/s. Justin said that this is determined by EEPROM and /proc. I haven't
set anything in /proc, so I guess we can rule out the BIOS setting
limitation.

The "when" part above is strange. Now I don't have the drive connected,
aic7xxx is loaded, but I see neither kernel messages in log, nor
/proc/aic7xxx. I'm running Debian sid's 2.4.18-4-k7. rmmod, modprobe
don't help. At the last boot the module was also loaded, no messages,
but rmmod, modprobe did help. The red LED named "DS1" is constantly lit.
Should I throw the card away? Or could it be anything else (power
supply???)?


> Also with Single Ended, the SCSI Cable Length can be critical.
> Depending on a number of factors, going more than 2 meters may add to
> the problem.

1.2 m, four 68-pin connectors for drives, black box at the end saying
"Foxconn" and "Ultra 320" (terminator?), the drive connected to the last
entry before the terminator ("far" from the controller).


> The SCA-1 Adapter may also be adding to the problem unless it is known
> to be able to work at the Ultra burst rate in Single Ended.

Hmm, specifically SE? The adapter claims to be "Ultra4 320/m SCSI
compliant". I'm not sure what "/m" means. MHz? It doesn't have any
active components. One resistor goes from SCA-2 to the jumper named
"LED". There are also SYN, DLY, MTR, ID3-0 jumpers, none set.


> Also verify how you have the terminations. If these are the only two
> devices, the 2940UW must have its terminations turned on (automatic
> may be ok) and there should be a termination at the drive.

The disk is the only device on the bus. If the black box is a
terminator, then I guess I don't need termination on the drive. The
drive is branded Sun and doesn't have any jumpers. I don't know whether
one of the jumpers on the adapter is for termination; I assume none.

At the other end, the controller has three connectors, two internal and
one external. I guess it should be terminated. There are six jumper-like
pins, four named J3, and two named J4.
http://download.adaptec.com/pdfs/user_guides/p2940uw_ug.pdf doesn't
mention anything about them, but says the termination can be set in BIOS
to Auto, Enabled, or Disabled. Is there a way to check the setting?


> I believe the Fujitsu MAN3184M is Ultra160 Low Voltage Differential 
> (LVD), and capable of automatically going down to Single Ended 
> communications from LVD communications, like almost all LVD devices, but 
> its not being used to its full potential by doing so.

Yes.


> Changing to the 29160 controller which is Low Voltage Dfferential
> (LVD) will help immensely in terms of being able to operate at a
> faster burst rate and being able to reliably support longer SCSI cable
> lengths.

Do you think this will work properly with the adapter? I had stability
problems with a similar adapter, AHA-2940UW, and the same drive
(although that one was not claiming Ultra 320 compliancy).


With kind regards,
-- 
Baurzhan Ismagulov
http://www.kz-easy.com/