DDS Tape problems

[Jerry McAllister]

> 
> Alex Zbyslaw wrote:
> > Pavel Duda wrote:
> > 
> >> Hi,
> >> I have problem with my DDS-3 type drive. I'm able to write on it but 
> >> not read data back. If I try to read them I get card dump and tape 
> >> drive hangs up. I have tried to upgrade firmware but problem remains. 
> >> Does somebody have experience with this ?

We have had a lot of experience with seeing similar problems, but little 
with solving it.   We have about 75 systems with mostly DDS-3 some are 
DDS-4. All Are SCSI.   All were on Dell Poweredge machines and are which 
ever vendor OEM model they were installing at the moment - but we couldn't 
seem to identify a clear difference from one model to the next.  

More than half seem to have been working fine for several years.
The rest have continual problems with symptoms similar to yours - 
it appears to write OK, but the tape is unreadable.   There appears to
be stuff on the tape but it is junk.  I say this because skips and
rewinds take about the amount of time I would expect,  but of course
that is not a definitive test.   Also, sometimes I can cat or dd a file
off the tape that is junk (eg the file is junk - not readable as anything.  
But often I cannot get anything at all.   Some got errors during the write.

I think there are multiple problems with the DDS drives, some of which 
may be their own hardware on internal control and some may be the 
SCSI controller or the drivers, but I have never been able to pin 
anything down and after asking several questions on the lists over
several years, have had no response other than some people agreeing
and some stabs with additional questions to answer that all went nowhere.

In a couple of cases, getting the drive replaced seemed to fix the
problem.   I believe the ones that warranty replacement helped were the
ones that failed during write.    In others I don't think rplacement helped.   
Some sites have upgraded to DLT.

I know none of this helps much toward solving the problem, but I post
this response for moral support and in hopes of jogging someone who
might know more about these things.

////jerry


> >> My specs :
> >> FreeBSD 5.2.1, generic kernel, x86 (P3), SCSI card is Adaptec AHA2940 
> >> and tape drive Python 04106.
> > 
> > Not terribly helpful, but I have a DAT2 working with an Adaptec 2940A.  
> > It's worked since forever and is fine with 5.4 though I never ran 
> > 5.1/2/3.  Is the machine it's attached to dual-boot?  I.e. can you test 
> > the tape drive in Windows, or Linux for example?  (Well, they have to be 
> > good for something :-))   Is this a recent problem or is this the first 
> > time you've tried using this drive?  Can you try another SCSI adapter?  
> > I've run mine (for testing only) off the cheapest rubbish I got free 
> > with a SCSI CDRW and it was fine.
> 
> I was trying to use Tekram SCSI adapter with same result. I have taken 
> this DDS tape from my AIX machine (netfinity) where it was working wo 
> problems.
> 
> > The only other guess would be termination.  Has anything else on your 
> > SCSI chain changed?  Is the terminator properly plugged in?
> 
> Termination should be fine. I have tried both variants - termination on 
> tape and termination via active terminator on cable.
> 
> > --Alex
> >