Cant read DLT tape from another machine

[Kurtkarl]

We have 2 machines and here???s the configurations

Machine A
Model = 9000/800/N4000-55 64-bit
Hpux = 11.0
DLT = /dev/rmt/c3t13d2BESTn

Machine B = 9000/800/K360 32-bit
Model = 9000/800/K360
Hpux = 11.0
DLT = /dev/rmt/2m

- On Machine A, I can create and read tar
tapes created by itself
- I can also read any tar tapes created by
Machine B.

- On Machine B, I can create and read any
tapes created by itself.
- BUT I CANT read any tar tape created by
Machine A. Error (Tar: tape read error)

I'm using the same DLT tapes on both machines.

Any thoughts?

Thanks
Joey

[Michael Tully]

Hi,

Are they the same tape drive model?

If on system B you have a DLT 4000
you will not be able to read tapes
that have been created on a DLT 8000.
You can set up a special device in
order to do so. If on the other hand
both systems do in fact have the same
tape drive model, I suspect that System
B's drive has a slightly different
alignment. I've not seen this on a DLT
but on many occassions on a DDS.

-Michael

[A. Clay Stephenson]

Hi:

First thought,

Are the two tape drives both DLT8000's, DLT7000's, or DLT4000's. The higher DLT's can read the lower but the converse is not true.

[Kurtkarl]

Machine A is a "Quantum DLT 8000"
Machine B is a "Quantum DLT 4000"

Since they are not the same, are there any workaround that we can do inorder for machine B to read tape created by Machine A? is there a patch or can I assign another device file for machine B?

Again, thanks for the quick response
Joey

[Michael Tully · Accepted solution]

You could create a device to do this, though
I'm not sure it will work. I've seen a
device created for a DLT 7000 so that
it writes in DLT 4000 format, but DLT8000
to DLT 4000 is again different. I'll try
and find something for you.

-Michael

[S.K. Chan]

The only way for you to be able to read a DLT8000 tape on a DLT4000 drive is if you have setup DLT8000 drive to write as DLT4000 format at the first place. You can actually create additional DLT4000 formatted device file which you can use to write to from DLT8000 drive.

Example :-
# mksf -H 4/4.3.0 -d stape -b DLT_81633_64c /dev/rmt/DLT4000_compressed
# mksf -H 4/4.3.0 -d stape -b DLT_81633_64 /dev/rmt/DLT4000_uncompressed

In your scenario reading the DLT8000 tape on DLT4000 drive is not possible.

[Michael Tully]

Here's what I found:

HTH
-Michael

I've picked this case where you want to write to the tape in a DLT7000 format on a DLT 8000 for restoration onto another server which has a DLT7000. Below I'm assuming that /dev/rmt/0m maps to the DLT8000 device.
If not, please change this reference to the appropriate device file.

First of all, in order to allow the stape driver to recognize the Quantum DLT8000 tape devices, you must apply patch PHKL_22856 (HPUX 11) including dependencies. These patches are available from the ITRC Resource Centre at
http://itrc.hp.com/wpsl/bin/doc.pl/screen=wpslSrchHPUXpatches/?OS=HP-UX

You will need to ensure that the tape devices in /dev to are recreated to cater for the updated stape device driver and DLT8000 capabilities:

# mksf -C tape

The device files /dev/rmt/0m will now be at the default density for a DLT8000 which is higher than that for the DLT7000 so using these will not provide interoperability between the different drives. Type the following to create new device files for this device at the DL7000 density setting. The
hardware path specified with the -H can be obtained by running 'lssf /dev/rmt/0m'.

# mksf -C tape -H 0/12.3.0 -b 133 -c 1 /dev/rmt/0m-DLT7000_mode

Perform testing as required to confirm that this *new* device file does
perform as required:
eg: tar some files to the DLT8000 device

# tar -cvf /dev/rmt/0m-DLT7000_mode ./tmp

Rewind the tape and remove it from the DLT8000 device. Attempt to restore the tape on a DLT7000 device (assuming 1m is a DLT7000 device):

# mt -t /dev/rmt/0m-DLT7000_mode
# cd /tmp; tar -xvf /dev/rmt/1m

[A. Clay Stephenson]

Hi:

I might suggest a Plan B that might be the best of both worlds. This does assume that both machines are fairly near each other and that the N-box is using a HVD SCSI interface.
If that is the case, then why not but both drives on the same bus but with the convention that at most ONE drive is active at any time.

K-box SCSI ID 6 --- DLT4K ---- DLT8K --- N-box SCSI ID 7.

If you can limit the total bus length to no more than 25m, this will work and, in fact, I use a configuration like this everyday. In this way you can make device nodes for both drives on both hosts.

Thinking outside the box, Clay

[Michael Tully]

Clay,

Interesting concept. In your environment
can you create/boot an ignite tape image.
This could solve a problem of mine where
I have lot's of servers not enough tape
drives and HBA's ?

-Michael

[A. Clay Stephenson]

Hi Michael:

I don't know but I suspect that it will. In my case, all my boxes have DDS drives and that is my medium for make_tape_recovery. My use of the DLT drives is backup. During the night, I use the the device nodes attached to Server A ,where most of the data resides, for backup. During the day, I use the device nodes attached to Server B to make copies of the previous night's OmniBack media for offsite export. This allows me to backup directly from the production servers at night but not load them during the day doing the copies.

Regards, Clay