Conference ssag::ask_ssag

6436.0. "KZPSM questions" by DECIDE::MOFFITT () Fri Feb 28 1997 09:12

I'm trying to support a customer (Lawrence Berkeley Labs) who are seeing 
pretty poor performance on a mongrel AlphaServer 2100 they've built 
themselves. The problem is that I'm about 1,000 miles away and can must 
guess at what they're running into. 

Their complaint is is that as they add drives to their external SCSI bus,
performance drops significantly. From what I can tell, they've written a 
VERY simple benchmark that writes a file to a device. As they add drives 
they run the same benchmark and write to multiple drives. Performance drops 
from around 4 MB/sec for 1 drive to around 1 MB/sec once they try to write 
to 3 or more drives. These are aggregate numbers. 

The system is an older AlphaServer 2100 4/275 with multiple CPUs. I/O is to 
a KZPSM connected to a third party storage subsystem composed of Seagate 
Baracuda 4.3 GB drives. I'm pretty sure the storage subsystem is functional 
- they disconnect the cable from the back of the AlphaServer, connect it 
into a Sun SparcServer and they see performance scale almost linearly with 
additional drives.

I THINK I have a termination problem with the KZPSM. Yesterday as they were 
playing with the machine they noticed that it would hang during boot while 
trying to probe for devices on the KZPSM IF the storage box was not 
attached. If they attached the box thesystem would boot but performance on 
the bus would start to drop again as additional drives were added.

I have absolutely no documentation on the KZPSM but they claim that the 
softterm parameter is set to "diff" (differential?). Shouldn't it be set to 
simply "on"? It's my understanding that the KZPSM isn't a differential 
device. What happens when you set softterm to "diff"?

Where might I find some documentation on this adapter? Is it similar enough 
to the KZPDA to allow me to use the KZPDA installation guide (which I do 
have)? ANd finally - the KZPSM is supported on the AlphaServer 2100 4/275 
isn't it? O/S is DU 4.0B

Thanks for any help...

enjoy,
tim m.