Last disk in SCSI chain

[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 for boot disks)' 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.
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 patch bundle of March 2003, hopefully the last one.

The only suspect I have are about the drivers included in the hpux kernel and about eventual SCSI patches I have lost.

Maybe someone can help me ? Even suggesting me which drivers to activate in the kernel.

Thank you in advance

[Amit Dixit_2]

Eric,
Maybe I sound stupid, but are you sure after
changing the the positions you connected
them well.

[enrico.nic]

I am almost shure, since the initial SEArch command returns all the 6 scsi ids (DVD + DAT + 4 disks) correctly

[Sanjay_6]

Hi,

Instead of doing a ioscan -fnC disk, can you try ioscan -fnH H/W_path. Here H.W_path is the path of the scsi channel. Can you attach the output of ioscan -fn if possiblem.

Hope this helps.

regds

[enrico.nic]

# ioscan -fnH 8/16/5
Class I H/W Path Driver S/W State H/W Type Description
=====================================================================
ext_bus 1 8/16/5 c720 CLAIMED INTERFACE Built-in SCSI
target 3 8/16/5.0 tgt CLAIMED DEVICE
tape 0 8/16/5.0.0 stape CLAIMED DEVICE HP C1537A
/dev/rmt/0m /dev/rmt/c1t0d0BESTn
/dev/rmt/0mb /dev/rmt/c1t0d0BESTnb
/dev/rmt/0mn /dev/rmt/c1t0d0DDS
/dev/rmt/0mnb /dev/rmt/c1t0d0DDSb
/dev/rmt/c1t0d0BEST /dev/rmt/c1t0d0DDSn
/dev/rmt/c1t0d0BESTb /dev/rmt/c1t0d0DDSnb
target 4 8/16/5.2 tgt CLAIMED DEVICE
disk 1 8/16/5.2.0 sdisk CLAIMED DEVICE HP DVD-ROM 6x/32x
/dev/dsk/c1t2d0 /dev/rdsk/c1t2d0
target 5 8/16/5.3 tgt CLAIMED DEVICE
disk 3 8/16/5.3.0 sdisk CLAIMED DEVICE HITACHI HUS157336EL3600
/dev/dsk/c1t3d0 /dev/rdsk/c1t3d0
target 6 8/16/5.4 tgt CLAIMED DEVICE
disk 4 8/16/5.4.0 sdisk CLAIMED DEVICE HITACHI HUS157336EL3600
/dev/dsk/c1t4d0 /dev/rdsk/c1t4d0
target 7 8/16/5.5 tgt CLAIMED DEVICE
disk 5 8/16/5.5.0 sdisk CLAIMED DEVICE HITACHI HUS157336EL3600
/dev/dsk/c1t5d0 /dev/rdsk/c1t5d0
target 8 8/16/5.7 tgt CLAIMED DEVICE
ctl 1 8/16/5.7.0 sctl CLAIMED DEVICE Initiator
/dev/rscsi/c1t7d0

The mismatched disk is at SCSI ID 8/16/5.6.0.
If I change the '6' in '1' the behaviour is the same, the disk at SCSI ID 1 (last in chain) becomes invisible.

Thank you
Enrico

[Sanjay_6]

Hi,

Are we sure the disk that is not seen is a working disk. what if you removed one of the disk that you can see in ioscan, say the one at 4, put id 4 on this disk which is not seen and plug it into the same channel / slot where the current disk at id 4 is sitting.

Hope this helps.

Regds

[enrico.nic]

I tried to exchange the disks with ID 3 and 6 as position, and again the last disk in the chain (id 3) became invisible.
The 4 disks are physically OK, the problem seems to be related with the last position in the chain.

[Gennaro Tarone_2]

Sounds like you have a hardware problem. Possibly a bad SCSI connection/disk slot for the last drive in your chain of disks. What kind of disk enclosure are you using & what kind of disks? Do you have another open SCSI connection to attach the disk to? Also, have you checked all the SCSI devices SCSI ID physically & not just through the SEA command? I have seen devices give out false SCSI ID's if one of the other devices is set to the same SCSI ID. Lastly while checking the SCSI ID's physically also check the other jumper settings of the disks. The disk just prior to the missing disk may have its "term power" jumperset to on.

[enrico.nic]

The reseller told me he already attached successfully this box to a HP 9000 D380 (the same machine). The only physical difference between the two HP boxes, he said, are the two scsi devices (DVD and DAT/DDS) attached to the same controller: these are present on my system, absent in his system. For this reason I tried to reduce the chain length - around 50 cm less with the external SCSI cable, around 20 cm less putting an internal scsi terminator instead of the original external one.

The last thing I've done is trying to activate drivers disc1, disc3, disc4, scsi1 and scsi3 that were out of the kernel before, but without luck.

[Hein van den Heuvel]

>> 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.

That is NOT acceptable and bound to cause signal integrety problems.
SCSI cables MUST be terminated at both ends and only at both ends.
Not 'almost at the end'
Not just at one end, not at both end and one more on the adapter.
You are only allowed inches unterminated: the distance from the cable/connector to the circuitry.

Finally... have you tried an alternate cable?

Cheers,
Hein.

[Sยภเl Kย๓คг]

Enrico Nicolis
Remove the DAT and DVD ,connect the HDDs at in fashion that it starts from the beginning of the SCSI cable.Put the terminator at the end of the scsi ribbon.
try it out
regards
SK

[enrico.nic]

I already tried two alternate cables, for the internal and external cables.
At present, rather than having a machine without DAT and DVD, I would prefer to find out a different box.
The reseller is suggesting to buy another (scsi single ended) controller.

[doug mielke]

any devices after the terminator should not be seen.
Also, if there is a slow (i.e. tape) device, place this at the end of the chain.

[Dave Unverhau_1]

Enrico,

It sure sounds like the problem is in the external chassis. Again, what is the make and model of the chassis?

Do you have a PC with a single-ended SCSI HBA that you could attach this chassis to, just to see how it behaves?

Also, I agree with Sunilkumar...try booting the system with the DVD and DDS drives disconnected *just to see how the disks behave*. If you still can't see all four drives, your problem is almost certainly in the external chassis.

I have seen external chassis with flaky power supplies behave in this way. Also, the SCSI harness in the external chassis could be causing the problem. It really doesn't seem to be a problem with anything else...

Best Regards,

Dave