Hi Paul,

you are right in terms of operating system. Its Linux.
It seems to be a problem with the amanda configuration. And it might be the
HW-compression of the drive. But I've deactivated the HW-compression at the
drive itself and the checks with mt -f /dev/st0 datcompression says that
the compression is off...
SW-compression I don't use actually to ensure that I don't run into trouble
with this feature interfeing other problems ...

Are there any problems that kind reported earlier?


                                                                                
                                                                    
                                                                                
                                                                    
            Paul Bijnens                      To:   Arne.Briesenick.ext AT 
deutsche-boerse DOT com                                .                        
            <paul.bijnens AT xplanation DOT co       cc:   amanda-users AT 
amanda DOT org                                                                  
       
            m>                                Subject:    Re: strangeTape size 
problem [Deutsche Boerse Systems:Virus                               
                                         checked]                               
                                                                    
            28.04.2004 12:15                                                    
                                                                    
                                                                                
                                                                    
                                                                                
                                                                    




Arne.Briesenick.ext AT deutsche-boerse DOT com wrote:

> I've a problem with amanda (2.4.4p1) on my TapeSet1. It reports an error
> when writing a single (19G) file to tape (20G DLT4) on a Quantum DLT4000
> without copression.
> The most strange thing is, that with the parameters from amtapetype -
which
> was horrible long time running - that single file does not fit on the
tape.
> BUT, when I write it explicit by dd if=dumpfile of=/dev/st0 it fits on
the
> same Tape and there is a real 1G free space at the end of the tape.
> So whats the problem with the configuration of amanda?

You didn't tell what OS.  Is it Linux?
In that case it could well be that the following scenario happened:
1. you had first the tapedrive in compressed mode, the default, and
    tested some things using that tape.  Now the first bytes on that
    tape are written in hardware compressed mode.
2. You find out how to disable hardware compression, by using
    the "mt" command, and you disable hw compr with it.
3. Then you label the tape with "amlabel".
4. You run amdump, and the tape overflows...

You may have the impression that after step 2, the drive had
hardware compression off.  This is not completely true in Linux.

When you immediately write to the tape, that is true.
But when you insert a tape, and you read something on it, the drive
automatically adjusts to whatever mode it was written to.

It now happens that amlabel first reads the tape, to verify if there
is already a label on it, and by doing this, the drive adjusts itself
to hardware compression ON.  The label is then written in hardware
compression ON again.
When you run amdump, the same thing happens: amanda verifies the
label, and adjusts the drive to hardware compression ON if needed.
Anything written after it, will be done IN THAT MODE.

To get out of it, you have to disable hardware compression, and then
write to tape WITHOUT reading anything.  That is probably what you did
when trying to write the backup image with "dd".

You can verify this auto-swich to hardware compression with
the command "mt status" before and after reading something
from the tape.

It could just as well be something completely different, e.g. a write
error to tape?  Something in the system logs about this?

PS. about the horrible long time for amtapetype: did you specify
     the "-e 20g" as indicated in the man page?  In that case it would
     take about 5 hours for writing the two passes.

--
Paul Bijnens, Xplanation                            Tel  +32 16 397.511
Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM    Fax  +32 16 397.512
http://www.xplanation.com/          email:  Paul.Bijnens AT xplanation DOT com
***********************************************************************
* I think I've got the hang of it now:  exit, ^D, ^C, ^\, ^Z, ^Q, F6, *
* quit,  ZZ, :q, :q!,  M-Z, ^X^C,  logoff, logout, close, bye,  /bye, *
* stop, end, F3, ~., ^]c, +++ ATH, disconnect, halt,  abort,  hangup, *
* PF4, F20, ^X^X, :D::D, KJOB, F14-f-e, F8-e,  kill -1 $$,  shutdown, *
* kill -9 1,  Alt-F4,  Ctrl-Alt-Del,  AltGr-NumLock,  Stop-A,  ...    *
* ...  "Are you sure?"  ...   YES   ...   Phew ...   I'm out          *
***********************************************************************



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