DLT4000 tape drives

[Linda Lux]

I have a K460 running 11.0 and have 2 DLT tapes drives hooked to it. I had one go bad, so I hot swapped it out with out realizing I could not do that. I ended up shutting down, power off box, power on, but system still doesn't open or identify the tape drives.
Where do I go from here?

[Pete Randall]

Check for SCSI ID conflicts. If you need to change the ID, you will have to power cycle the drive in order for it to take the new ID. Then do your ioscan and you should see the drive.


Pete

[Linda Lux]

I am new at this - what are some of the commands to do this?

[DCE]

Linda

ioscan -fnC tape
will list the available tape drives

you should see the drive and the device files
(i.e. /dev/rmt/0m)

If you have a SCSI address conflict, then you will not see one or both of the drives in listing

To change the SCSI address you have to physically move a setting on the actual drive. Look at the two drives in question and find out if they are both set to use the same number. If so, power down the system and change the setting on the "new" drive, then power up

[Pete Randall]

Linda,

Since the system can't see the drive, there are no commands. You have to physically look at the back of the drive to see what the SCSI ID is set to. There's a little window with a plus and a minus button. I would suggest making sure that the ID in the window is set to the same number as your previous drive. If you don't know what the previous drive was set to, you will need to analyze ioscan output looking for the SCSI IDs of devices on the same path as the drive to make sure you're not duplicating.

I have previously swapped these out "hot" and never had any problem. The symptom you describe simply screams SCSI ID conflict!!


Pete

[Linda Lux]

The old drive was set at 4, so that is what I set the new drive as. The other has 5 on the back

Linda

[Patrick Wallek]

You need to power the drive off and back on for the new id to take effect.

Then try an 'ioscan -fnC tape' and see what output you get.

[Linda Lux]

My ioscan looks like this:
10/16/12 ext_busHP 28696A - Wide SCSI ID=6
10/16/12.0 unknown
10/16/12.1 unknown
10/16/12.2 unknown
10/16/12.3 unknown
10/16/12.7 unknown
10/16/12.8 unknown
10/16/12.9 unknown
10/16/12.10 unknown
10/16/12.11 unknown
10/16/12.12 unknown
10/16/12.13 unknown
10/16/12.14 unknown
10/16/12.15 unknown

[A. Clay Stephenson]

Are you certain that the replacement DLT4000 drive is compatible? Specfically, do you know that it is a HVD scsi device because not all DLT4000's are? If you installed a non-HVD device on an HVD SCSI bus then you could have damaged the HBA, terminators, and any other devices on the bus. Normally, while certainly not recommended, hot-swapping external tape drives does not cause problems or damage equipment. I do it rather routinely to replace failed tape drives as long as only tape drives are on the bus and that the bus itself is idle at the time. Have you made certain that the bus is properly terminated -- at the physical ends of the bus? It's possible that you have enabled termination on a drive in the middle of a bus. It's also possible that you blew the termination power fuse on the HBA --- that's not uncommon especially if the pins might be slightly bent. As a matter of course, I would check each connection for bent pins. It's really easy to bend a few on these connectors.

[Linda Lux]

I have the cable form the HP box to the bottom connector of one drive, then a cable from the top connector to the top connector of the second drive (the one I replcaed), then a terminator on the bottom connector fo the second.
I have already checked the pins and none are bent.

[Linda Lux]

I asked my supplier and they are suppose to be HBV

[Linda Lux]

sorry - HVD is what I meant

[Linda Lux]

If I blew the fuse on the card wouldn't it show amber light instead of green, or not show at all. Ioscan sees the card yet.

[A. Clay Stephenson]

10/16/12.7 unknown --- This entry looks extremely suspicious because it implies that another controller is on this bus. Is that the case? I note that your HBA's SCSI ID is set to 6 where it is normally 7 --- again, unless there are two controllers on this bus.

[Linda Lux]

The DLT drives are daisy chained.
Linda

[A. Clay Stephenson]

Oh, and you have way too many devices on this bus. The maximum number of DLT4000's on a HVD/FWD bus is 2. That will completely saturate the bus. If DLT's are not supplied with data fast enough to allow them to stream, the throughput drops but a factor of 100 or so. Normally DLT's are installed on a dedicated bus. This isn't your problem at the moment but you are going to be very disappointed in performance if, and when, you get the drives recogized.


The Green TERM PWR LED on the 28696 indicates that the fuse is not blown. I assume that you have the stape and scsi3 drivers "In" the kernel.

[DCE]

unknown usually implies that the stape or scsi driver is not in the kernel. Did someone regen the kernel and remove the driver? (the kernel does not recognize the tape drive - hence unknown)

The usual practical limit for high spped tape drives per bus is two - even that sometimes adversely impacts backup speeds. You may want to consider reducing the number of devices on this channel.

[Linda Lux]

I only have the 2 DLT's daisy chained together.
This is how it has always been. I am going to shut the system off, unhook the daisy chain, terminate the one connector, turn system back on to see if I can at least have one good tape drive to do my backup.

[Linda Lux]

stape and scsi3 are in the kernel
Linda

[A. Clay Stephenson]

My ioscan looks like this:
10/16/12 ext_busHP 28696A - Wide SCSI ID=6
10/16/12.0 unknown
10/16/12.1 unknown
10/16/12.2 unknown
10/16/12.3 unknown
10/16/12.7 unknown
10/16/12.8 unknown
10/16/12.9 unknown
10/16/12.10 unknown
10/16/12.11 unknown
10/16/12.12 unknown
10/16/12.13 unknown
10/16/12.14 unknown
10/16/12.15 unknown

If you have only 2 DLT4000's on this bus then something is very wrong. You are seeing far too many devices. I would not make the assumption that the external thumbwheel switchg that is used to set the SCSI ID is actually connected to the drive. If that were left uncoonected on either drive then the SCSI ID is indeterminate. It might even be hard jumpered on the drive itself so that just because you don't think you have a SCSI ID conflicts doesn't mean that you don't have one. If this is a single HBA bus, then your 28696's ID should be set to the highest priority, 7.

[Linda Lux]

I am not a sys admin by trade or training, so you will have to explain in "layman" terms what you have just told me about the scsi id=7

Linda

[Linda Lux]

Could some of these have been created when I shut the system off and back on?
Linda

[DCE]

What form of iscan did you use?

ioscan -fn will show all of the devices on the system

Rebooting the system without the tape devices should make the unknown devices disappear.

Did you try shutting the system down, removing the new tape drive, terminating the old drive where it was daisychained to the new one, and then bring the system up

Hopefully an ioscan -fnC tape will show the one good tape drive

[A. Clay Stephenson]

Okay, I'm doing this from memory but:

1) Shutdown and remove the HBA (taking normal static electrical precautions).
2) There is a small DIP switch with 8 individual switches. The leftmost 4 switches
control the SCSI ID.

For SCSI ID 7:
Sw. 1 (1) (LSB) Should be set to "1".
Sw. 2 (2) Should be set to "1".
Sw. 3 (4) Should be set to "1".
Sw. 4 (8) Should be set to "0".

Because you are currently at 6, the only change needed is setting Sw. 1 to "1".

There are also 3 Terminating Resistor Packs adjacent to the DIP switch. If these are missing then the HBA is not terminated.

3) Reinsert the HBA and boot. I would connect nothing to the card and do an ioscan -fn --- only the HBA should appear in the listing. I would then connect 1 tapes drive and make sure that a terminator is on this end of the bus and do another ioscan. If normal add the 2nd tape drive and repeat.

[Linda Lux]

i just used straight ioscan

if i do ioscan -fnC tape
I only see the internal DAT drive

I am going to do the tape drive shutoff, system shutoff, hook only the good drive up, and start system up - I hope to see one good tape drive.

Linda