November 24, 2015
The Wide World of Connecting Storage
IO used to be more complex for IT. Sure, the array of choices for disk is vast today. But in the era when 3000s used to think they were lucky to get SCSI plugged into them, configuring disk connections was not simple. HP-IB protocol, built to link HP's instruments, was simple, used for all HP devices, and slow. But it was integrated and seamless compared to the SCSI of single-ended, fast/wide, and Ultra Fast.
Such was the case for one 3000 manager seeking advice from his colleagues. You never think about these things on a 3000 until the hardware breaks. Or backups fail. Or storage media gets rare. Aging hardware is one of several issues that require expertise, even if a 3000 runs the ultimate 7.5 version of MPE/iX. Our manager hunted for his help on the longest-running 3000 classroom in the world, the HP3000-L mailing list.
A single-CPU A-Class was moving away from DDS technology, the DDS-3 that was first launched in the '90s. There are other options for 3000 tape backup. But these options include single-ended, fast/wide, and other cable and termination combinations. DLT technology, introduced more recently but still a 1990s choice, runs with HP 3000s. It helps to get the ends right, though, if DLT is to have a new beginning on an old-school 3000.
"Until now they have done their backup on DDS," a manager talking to the 3000 newsgroup explained. "Lately they had a failure on the DDS drive, and have realized that it is getting difficult to get new tapes. They have decided to move to DLT8000, model C6378A, and have bought two of them. One is supposed to go live on the 3000, and the other to be stored as a spare device."
The DLT is hooked to the Ultra Wide SCSI interface on the A-Class. But ODE/Mapper doesn't recognize the device."
There was an error, and no DLT joy. Soon enough, one veteran consultant said, "You will have trouble connecting a fast wide SCSI device to an ultra-wide SCSI controller." It wasn't a rookie mistake, but the veterans who still prowl 3000-L had a solution and even a link to an inexpensive fix. So it goes, here in the fifth decade of HP 3000 mission-critical service. Answers are everywhere.This wasn't an inexperienced 3000 pro, it seemed, when reading that he tried to "add the device in IOCONFIG by adding first the path 0/0/1/0.2, and then the device with the command: ad 8;path=0/0/1/0.2.0;ID=dlt;mode=autoreply."
SCSI on the 3000 sure isn't the world of USB, where just 2.0 and 3.0 cover the scope of IO choices. A $59 adapter card connected that DLT to the 3000. The IO challenge also prompted advice even a pro might not know — making a case for having fresher hardware than HP's to run MPE.
There was advice about using Mapper on the 3000 to troubleshoot an IO device from Michalis Melis.
Normally the path and the device should be recognized by running ODE/ Mapper without even loading the operating system. You do not have to go to SYSGEN. If Mapper fails you have a problem before the OS loads.
Craig Lalley made the link between two incompatible kinds of SCSI interfaces.
You are trying to hook up a Fast/Wide SCSI device to an Ultrawide interface. The C6378A can only connect to a HVD Fast Wide SCSI interface (A4800A SCSI card comes to mind). Remember, the A-class does not support Dual-Head cards, so your only option is A4800A. You need either a DLT8000 with a Fast-Wide interface, or you need a cheap A4800A HVD (High Voltage Differential) SCSI card. You can daisy chain devices to the card, but I would only use one tape at a time.
Lalley also tipped his hat to Keven Miller, who supplied the link to that $59 adapter card.
Then Denys Beauchemin, who has been among one of the more prolific contributors to the 3000-L, delivered detailed advice about connecting backup devices. His background reaches back to the first decade of 3000 use, including years spent with Hi-Comp on backup software development.
Fast/Wide SCSI (FWSCSI) is essentially HVD SCSI on SCSI-2 standard. This means that the signal is a differential in the voltage between various wires (HVD is High Voltage Differential) and Ultrawide SCSI is SE (Single Ended) SCSI, on the SCSI-2 standard which makes is wide (16 bits), like the FWSCSI.
So what is needed is a converter to power the signal from the Ultra Wide SCSI interface on your server to the FWSCSI interface on the DLT device. I have a number of those somewhere here, but they were for SE SCSI, not UltraSCSI. They might work for that, since all they did was provide the powered signal and the cable is the one that converted from wide to narrow.
Another thing to consider is that since HP nicely crippled the A-class, that 3000 system would not be able to keep the DLT8000 streaming. And that device hates not streaming, so much so that it will enter shoeshine mode and perform abysmally. Just a parting gift from HP to the MPE community. You should hear what they're doing to the VMS crowd.
That last comment comes from Beauchemin's current duties as migration manager for the OpenVMS users who are leaving that platform. VMS had a steady Internet community to help Digital users, just as the 3000 has 3000-L. People like Beauchemin, largely working outside the 3000 world, are still providing advice for homesteaders -- even while assisting in migrations. After migration there is much to manage, but simply migrating off Hewlett-Packard's 3000 hardware makes using MPE/iX less complex.
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