SCSI disks

[enrico.nic]

Hi all,

I am encountering a strange problem with an HP 9000 D320, HP-UX 11.0.
Having attached an external scsi disk array box, connected to the machine through the single ended SCSI connector (the controller that already has the DVD and DAT units), I see the correct SCSI IDs through the initial ISL prompt. The 'SEA(rch)' command correctly identifies the four (identical) new disks.
But after the boot, an
# ioscan -fnC disk
command reports only three physical disks. After changing the position of the disks, I noticed that the system simply refuses to identify the last disk of the SCSI chain, and that this is completely independent from the SCSI id given to that disk. I tried to reduce the length of the SCSI chain, but nothing happened.

Has any of you an idea of the possible reason ?

Thank you in advance

Enrico

[Sridhar Bhaskarla]

Hi Enrico,

I remembered to have seen this problem a very long back. I believe the terminator was the problem if I remember correctly. If the scsi- ids are unique in the chain, then I would check the terminator.

-Sri

[A. Clay Stephenson]

Since you didn't bother to identify the disks or the array (JBOD?) it's difficult to be specific. My best guess is that your bus is not terminated in exactly two place (on the physical ends of the bus) or that no device is supplying termination power. At least one device must supply this power. If any of you disks have the terminator resistor packs or jumpers enabled, you would see very strange behavior. Also, it's very easy to hit the SE SCSI bus length limits especially if you fail to count internal bus lengths.

[enrico.nic]

Some short additions I forgot in the first message.
I've changed the terminator and the scsi cable, trying to reduce the chain length. The terminator isn't external anymore but internal (close to the last disk in the chain), and the scsi cable is now a 50 cm long cable.
The disks are 4 internal, identical Hitachi HUS157336EL3600 (as reported by ioscan), that are 15 krpm disks, 36 Gb of capacity.
The disk array is a box with 7 places with 2 (hopefully redundant) power supplies, without any brand.

The system is patched with the latest patch bundle.

Thank you again

Enrico