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35G DLT written in 8000 readable in 7000?

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Jim Turner
Esteemed Contributor

35G DLT written in 8000 readable in 7000?

Good morning,

I am about to deal with a mixed environment of tape libraries. My 4/48 has Quantum DLT7000 drives and the new 6/100 has Quantum DLT8000 drives. It would be easiest for us to stick with the 35/70 DLT cart's, however I have concerns about a 35/70 from an 8000 being readable and writable in an 7000. I'm not up to the point of having both online to test myself yet.

These libraries will all be used with Omniback. So my question is this: If I format and/or write data to a 35/70 tape in an 8000 using Omniback, is it readable/writable in a 7000?


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paul courry
Honored Contributor

Re: 35G DLT written in 8000 readable in 7000?

I doubt it will be readable. The 8000 has a higher density than the 7000. Unless you delibretely lower the density so it is backwards compatible with the 7000 it will not be readable.

On the other hand, anything written with 4000 or 7000 DLT's will be readable by the 8000.
Michael Tully
Honored Contributor

Re: 35G DLT written in 8000 readable in 7000?

Hi Jim,

I had a similar query to this at the beginning
of the year and below is how it was handled.

This is quoted directly from the response that
I received, it should help you.

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.
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

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
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

# 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

Anyone for a Mutiny ?
Paul R. Dittrich
Esteemed Contributor

Re: 35G DLT written in 8000 readable in 7000?

Paul and Michael are correct.

The entire DLT series is upward-compatible for reading tapes from older units but they are not backward-compatible unless the newer(higher #) unit writes at the density of the older (lower #) unit.

So, an 8000 will have no problem reading a tape created on any older DLT drive, but an older drive will not read tapes created on the 8000 UNLESS you tell it to use the lower density (and waste capacity in the process).

Jim Turner
Esteemed Contributor

Re: 35G DLT written in 8000 readable in 7000?

Thanks everyone for the help!

As it turns out, our Ops folks have been purchasing 40/80 carts for a while. Color me stupid for not asking them first. They seem to work okay in the 7000's (albeit at less than max capacity), and obviously will work fine in the 8000's.

I simply created two new tape pools (one each center) for the tapes in the 6/100 libraries. I want to take advantage of the additional capacity and especially the additional speed (10MB/s vs. 5MB/s) of the 8000's. I'll adjust the backups as appropriate to use the new libraries and tapes. Our main focus right now is to convert backups whose tapes are taken off-site to backups that are *conducted* offsite via our WAN. We have two OC-3's between our centers. I'm certain our LAN folks can carve out a slice of that 311Mb/s for use as a VLAN between my Omniback switches.

The idea of humans not handling tapes and backups being conducted with drives/libraries at opposite centers makes our Disaster Recovery folks dizzy with delight.

Thanks again and sorry for the delayed points.

All the best!

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Ahmed Bedeir
Occasional Advisor

Re: 35G DLT written in 8000 readable in 7000?

does ayone know if it is possible for a DLT8000 to read DLT IV tapes written by a DLT1 drive (HP DLTvs80 specifically)?
Jan Klier
Respected Contributor

Re: 35G DLT written in 8000 readable in 7000?

The only cartridges that can be read by a VS80 drive are ones written on a VS80 drive or ones written with a DLT4000 drive. Cartridges written on DLT7000 and DLT8000 cannot be read.

And it is my understanding that cartridges written on a VS80 drive cannot be read by a DLT4000/7000/8000 drive.