Summary: read DLT8000 tape on DLT4000

Dear all,

Thanks for all who replied: 

Darren Dunham
Jay Lessert
Hichael Morton
Anand Chouthai
Geoff Reed
Peter Stokes
LHERCAUD

Jay Lessert and Darren Dunham gave me a very detail explanation about how to 
configure the tape driver on solaris. I attached their replies below.

Jay Lessert also recommends the following manual - 
http://www.quantum.com/NR/rdonlyres/ogtymm32ogk66q57nylwwnejnmbwf7xo2cyccshofrkg
ecbxp7d6ve3ynvvhn5fu4wzzvbe3lip7j/SunSPARCstationSunOS413.pdf

The solutions are:

1. write a DLT4000 tape head, which will define the tape density, then dump 
files on DLT8000 tape driver, which can be read out on DLT4000 driver.
2. change DLT8000 driver configuration in /kernel/drv/st.conf file and define a 
DLT4000 compatible device, I choose /dev/rmt/0ln as the compatible device name.


Both ways work for me. 

Cheers & have a good day,

carl


------From Jay Lessert-----

If the tape is already written, in DLT8000 mode (40GB native), no.  Period.

If the tape is yet-to-be written, yes.  Just make sure you write the
tape in DLT4000 (20GB native) mode, and the DLT4000 will read it just
fine.  I do this all the time for archive tapes because I have DLT4000
and DLT8000 drives, 20GB is enough, and I want to make sure I can read
the tape on any drive.

The DLT8000 drive can write in the following modes:

    DLT4000 (20GB native)
    DLT7000 (35GB native)
    DLT8000 (40GB native)

Each of these is available with/without compression, but you don't care
about that.

Unfortunately, the default Solaris setup for DLT8000 is:

    /dev/rmt/0l		35GB (DLT7000 uncompressed)

    /dev/rmt/0m		70GB (DLT7000 compressed)

    /dev/rmt/0h		40GB (DLT8000 uncompressed)

    /dev/rmt/0c		80GB (DLT8000 compressed)
    /dev/rmt/0u		80GB (DLT8000 compressed)

This does you no good, of course.  You would need a /kernel/drv/st.conf
setup for your DLT8000 that allows DLT4000 mode.

The enclosed PDF from Quantum tells you how to do that.

-----

---------From Darren Dunham-----
You'd probably have to modify your st.conf and construct a new line for
the DLT8000.

The lines in the st.conf contain (usually) four hex codes.  They're the
next to last things on the definition line.  As an example, the DLT7000
line looks like this..

#DLT7k-data =   1,0x38,0,0x1D639,4,0x82,0x83,0x84,0x85,2;

That maps to the 'l', 'm', 'h', and 'u/c' devices.
/dev/rmt/0l -> 0x82
          m -> 0x83
          h -> 0x84
        u/c -> 0x85

20G mode is 0x82.  20G w/compression is 0x83.  A DLT4000 drive should be
able to read either of them.

You'd want to construct a st.conf for your DLT8000 that contains at
least one of 0x82 or 0x83 and then use the correct device file to start
a tape.  Only the first write at the beginning of a tape can set the
density used.


In fact, you can use the fact that density on a DLT tape cannot be
changed except by the first write to help you.

You could start writing to the tape in the DLT4000, and then finish the
writes in the 8000.  Since it can't change the density, you should be
okay.  However, if the DLT8000 starts writing at the beginning of the
tape, it could change the density.
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