tape drive replacements not found with ioscan

[Ian Lochray]

I have an L2000 running HP-UX 11.11.  My DLT IV tape drive recently failed.  I have now had four replacements but none of them show up with ioscan.  I have restarted the server with each new drive and ensured that the SCSI id is the same as the one that broke.

How can I find out of this is a hardware compatibility issue?

P.S. This thread has been moved from Servers > General to HP 9000 - HP Forum Moderator

[Matti_Kurkela]

> How can I find out of this is a hardware compatibility issue?

Identifying the manufacturer and model of "your DLT IV tape drive" would be a nice start.

Likewise, knowing the exact type of the SCSI controller/HBA you've plugged it into would be a good thing too. Is it the integrated SCSI controller of the L2000 (on the core I/O card that is always in the bottom PCI slot, IIRC), or an add-on card?

Have you tried another SCSI card? Perhaps the failed tape drive damaged the card too.

Or perhaps another cable? If the existing cable was original to the L2000, it's probably old and stiff by now - if it has been damaged before, handling it now might have been enough to cause the cable to fail.

[Torsten.]

You could have bent pins if you use the evil 68pin vable.

[Ian Lochray]

I have now tried four different tape drives, most recently an HP Surestore 80.

I know it's not the card, cable or terminator as I have an identical server with an old Compaq DLT on it and, if I switch the tape drives between the machines, the old drive works fine on both but the new ones fail on both.

I find it hard to believe that I have been given four faulty tape drives which is what leads me to think that they are all new drives and may be incompatible with my old server.

[Torsten.]

Did you replace a HVD SCSI device with a LVD SCSI device (or vice versa)???

[Matti_Kurkela · Accepted solution]

According to this manual:

http://bizsupport1.austin.hp.com/bc/docs/support/SupportManual/lpg29237/lpg29237.pdf

the external HP Surestore 80 is a Low Voltage Differential (LVD) Ultra Wide SCSI-2 device.

On HP-UX hardware, the different SCSI bus types are often identified with particular colors:

• Single-Ended SCSI bus connectors often have a sticker with a yellow "SE" on black background
• High-Voltage Differential SCSI connectors often have a purple "DF" (or "HVD" on equipment manufactured after LVD became available) on black background.
• LVD SCSI connectors are marked with (if I recall correctly) green "LVD" on black background.

It is possible that your old SCSI card and the old Compaq DLT are both High Voltage Differential (HVD) devices; they used to be called just "Differential SCSI" before the LVD variety was developed. HVD SCSI equipment only works with other HVD SCSI equipment. LVD devices won't work when plugged into a HVD bus; they *should* be protected well enough to not be damaged by the HVD signal voltages, but they won't run. (In fact, the entire LVD/HVD SCSI bus will most likely be non-functional until the incompatible device is removed.)

It is possible to let the smoke out of Single-Ended SCSI devices by accidentally plugging them into a HVD SCSI bus.

LVD equipment should be downwards-compatible to SE SCSI, but this restricts the entire SCSI bus to SE speeds and cable lengths; on Ultra SCSI speeds, this means a maximum total bus length of only 1.5 m, which is rather inconvenient for external devices.

The type of the SCSI connector does not necessarily identify the SE/HVD/LVD bus type, so looking at the labels is required. A 68-pin external HD connector can be any type.

[Ian Lochray]

Bingo.  All the drives I have been sent are LVD and my SCSI bus is HVD.

Thank you to all who answered.

[TarunJain]

Good finding!