Unexpected busfree - termination problem?

[Fran Fabrizio]

I'm getting sets of errors that look like this:

Nov  6 09:35:13 keep kernel: (scsi2:A:0:0): Unexpected busfree in 
Data-out phase
Nov  6 09:35:13 keep kernel: SEQADDR == 0x9f

in my kernel log.  I have a Dell PowerEdge 2650 running Redhat 9, an 
Adaptec 39160, and aic7xxx upgraded to 6.3.6. 

I have no internal SCSI devices connected to this card.
On the first channel (A) of the card, I have two external devices, a 
Qualstar tape library, followed by a Sony SAIT tape drive, followed by a 
termination dongle (provided by Qualstar).
On the second channel (B) of the card, I have only one device attached, 
a StorCase DataStor DS570 disk array.  I have termination set to 
Automatic for both channels in the host adapter, and I have termination 
set to "On" in the DS570 configuration.

The log summary of these devices at boot time is included below.  The 
history of the DS570 is that it used to be hooked up to a different 
server which had a Megaraid controller in it and it worked fine for 
many, many months until failures started being tossed where the driver 
was queuing ABORT messages and then the device was being set offline 
after a bus reset.  So I moved the array to this new server and this 
different host adapter to try to figure out if it was the array or the 
adapter that is misbehaving.  I'm now seeing these Unexpected busfree 
errors from the Adaptec error, and I'm trying to determine if this means 
it really is the array and/or cabling to the array, or if this is 
unrelated to the other failures I was seeing and this new error is 
specific to the Adaptec host adapter. 

The DS570 doesn't detect anything wrong with its own SCSI controller or 
any of the drives in the array.  So, my latest thinking is that this 
could be a termination or possibly cabling problem.  I actually don't 
have a spare LVD cable at the moment but hope to get my hands on one 
early next week to give that a try, but is anyone familiar with these 
messages?  It would be good to know something even as general as "this 
usually points to a hardware issue" or "this is usually not a hardware 
issue."  I'm still a little wet behind the ears when it comes to 
debugging SCSI problems.  Any help is much appreciated!

Thanks,
Fran

---------------------------------------------------------------------------------------------------
scsi1 : Adaptec AIC7XXX EISA/VLB/PCI SCSI HBA DRIVER, Rev 6.3.6
        <Adaptec 3960D Ultra160 SCSI adapter>
        aic7899: Ultra160 Wide Channel A, SCSI Id=7, 32/253 SCBs
                                                                                                                                                             

scsi2 : Adaptec AIC7XXX EISA/VLB/PCI SCSI HBA DRIVER, Rev 6.3.6
        <Adaptec 3960D Ultra160 SCSI adapter>
        aic7899: Ultra160 Wide Channel B, SCSI Id=7, 32/253 SCBs
                                                                                                                                                             

blk: queue f7fade18, I/O limit 4095Mb (mask 0xffffffff)
scsi1:A:0:0: Tagged Queuing enabled.  Depth 32
(scsi1:A:0:0): refuses tagged commands.  Performing non-tagged I/O
(scsi2:A:0): 160.000MB/s transfers (80.000MHz DT, offset 31, 16bit)
(scsi1:A:1): 160.000MB/s transfers (80.000MHz DT, offset 126, 16bit)
  Vendor: QUALSTAR  Model: TLS-5433          Rev: 221a
  Type:   Medium Changer                     ANSI SCSI revision: 02
blk: queue f7fadc18, I/O limit 4095Mb (mask 0xffffffff)
  Vendor: SONY      Model: SDZ-100           Rev: 0101
  Type:   Sequential-Access                  ANSI SCSI revision: 04
blk: queue f7fb1e18, I/O limit 4095Mb (mask 0xffffffff)
  Vendor: DS570     Model:                   Rev: 0001
  Type:   Direct-Access                      ANSI SCSI revision: 03
blk: queue f7fad818, I/O limit 4095Mb (mask 0xffffffff)
scsi2:A:0:0: Tagged Queuing enabled.  Depth 32
Attached scsi disk sdc at scsi2, channel 0, id 0, lun 0
SCSI device sdc: 3418718208 512-byte hdwr sectors (1750384 MB)
 sdc: sdc1
-----------------------------------------------------------------------------------------------------