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SCSI External Backup tape not detected at startup

Posted on 2006-04-19
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Hi, I have a Certance external tape drive STD6401LW (seems to be a standard model number with a few companies , HP, Seagate, etc).  I've got two machines, and neither seem to be detecting the drive at startup (its terminated externally).  Am I wrong in thinking that I should at least see something at startup on the SCSI bus (just like if I had a hard disc attaced)?  Card is Adaptec.   I've tried it on two different machines and neither have them pop up on the bios screen.
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Question by:london_mccourt
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kdkirmse earned 472 total points
ID: 16488675
I have installed the same model on a machine and the scsi card bios, an adaptec, does detect the existance of the drive. Is there any other device connected to the card? Also, I believe that the drive can be internally terminated. Make sure that that jumper is not inabled as well.
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by:london_mccourt
ID: 16489030

Cheers for the quick reply kdkirmse, nope nothing else on the card, its an aic7xxx (so says Linux Ubunto), so you think that there is a jumper on the card which is terminating it anyway from the external ports?
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by:kdkirmse
ID: 16489430

I am more concerned about SCSI termination on the tape drive. SCSI HBAs often have a BIOS setting that allows the termination to be enabled and disabled. You need termination to be enable on both ends of the SCSI cable. Often this is implemented by enabling termination on the SCSI card  and the last drive in the chain.

You might also try entering the HBA BIOS and doing a device scan. It is possible on some cards to disable the automatic scanning for devices during boot.
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by:london_mccourt
ID: 16489472

Did a device scan after going into setup but nothing pop's up, says there is nothing on the bus.  Anyway of telling whether or nor the bus is properly terminated (with or without anything on it?)
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by:dovidmichel
dovidmichel earned 464 total points
ID: 16504702
The way to tell if the bus is properly terminated is the old fashion way by manually checking. Last device at each end of the bus should have a terminator or termination enabled if an internal device. All other devices should not have termination enabled.

In this case since it is the only device then as you said there is a terminator attached to the drive and then the other end will be the controller which controls termination via the controller setup program. Termination is set to automatic by default.

The drive is a narrow device so wide negotiation should be disabled in the controller setup.

Also since the drive is LVD both the controller and terminator need to be differential.
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by:london_mccourt
ID: 16505652

Can you explain this 'Also since the drive is LVD both the controller and terminator need to be differential.' please
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by:dovidmichel
ID: 16508691
The drive is listed as LVD Low Voltage Differential, so the controller and terminator have to be the same.

As per manufacter's web site:
 The Scorpion 40 external DDS-4 DAT is the most reliable DDS drive with an MTBF rating of 483,000 hours at 12% duty cycle. The Scorpion 40 stores up to 40GB (2:1 compression) of data per cartridge. With its LVD interface, the Scorpion 40 tranfers data at speeds up to 5.5 MB per second or 19.8 GB per hour greatly decreasing the time needed to back up your data.

For example the external connector on the Adaptec 29160 is LVD, and the external connector on the 29160N is just Ultra SCSI and not LVD.

Terminators also can be just plain SCSI or they can be LVD.  
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by:kdkirmse
ID: 16511868

Almost all LVD drives produced are actually LVD/MSE drives. A LVD drive should fall back to SE operation if
connected to a SE adaptor. Give how strange the SCSI standards are this may not always work in practice.

I believe the install I did with the STD6401LW was to a AHA2940 which is a SE HBA. That machine is at a
clients site so I cant easily check it.
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by:pgm554
pgm554 earned 464 total points
ID: 16521486
When the system boots,you should be able to hit CTL  A and get into the BIOS (this is an Adaptec OEM chipset)and give the EXACT model number of the controller chip.
Many of the older Adaptec chips are obsolete and are no longer supported.

From what I can tell,that chipset is  SE,so I agree with dovidmichel in that the issue is with the controller  not being compatible with an LVD device.
Plus LVD cables are different(and more expensive) than regular SCSI 3 cables

http://www.ramelectronics.net/html/scsi_internal_cables.html
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Author Comment

by:london_mccourt
ID: 16719794
Currently looking at the LVD stuff, going to talk to RAM Electronics and see what they say, thanks pqm554.  Also upp'ed the points value a bit, hang on in there, we'll figure it out.
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