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DLT rewind problems

Henrik Ejderholm
Occasional Visitor

DLT rewind problems

I have an L2000 server with several DLT7000 connected to it via SCSI. At some occasions I've experienced that the drive can rewind itself without notifying the backup s/w (in this case Veritas NetBackup). I've read some postings that this can happen upon a SCSI reset.

Q: Is there anything that can be done to prevent this behaviour? Can DLT drive be configured to not rewind itself, anything in HPUX that can be made? I have already configured EMS to not poll the drive.

Regards,

Henrik
5 REPLIES
Leif Halvarsson_2
Honored Contributor

Re: DLT rewind problems

Hi,
I am not sure about NetBackup but as you describe the problem I assume NetBackup uses norewinding device files, (for example /dev/rmt/0mn). The first thing to check is that nothing is wrong with the device file.

I don't think it is possible to change the drive behavior at SCSI reset.

What is the problem if the tape is rewinded ?
Michael Tully
Honored Contributor

Re: DLT rewind problems

Are you receiving any errors in your syslog file pertaining to 'lbolt'
These are general errors that you could receive, when there is a SCSI reset or timeout.

Do you have more than one DLT 7000 on a single chain?
If so, this could be your problem. DLT7000 and DLT8000 should never be shared on the same SCSI chain.
Anyone for a Mutiny ?
Vincent Farrugia
Honored Contributor

Re: DLT rewind problems

Hello,

Michael is right, if you have "several" DLT7000s connected to a single L2000, most probably you have 2 or more drives sharing a SCSI chain. If so, then this can cause a SCSI reset, especially if the drives on the same chain are working at the same time.

SCSI resets can also occur when you have a faulty cable or terminator. Check those as well (bent pins, overall quality of the cable etc.)

Mechanical damage on your tape drive might also result in a SCSI reset.

HTH,
Vince
Tape Drives RULE!!!
Henrik Ejderholm
Occasional Visitor

Re: DLT rewind problems

There is only one drive/scsi channel. The problem with having the tapedrive rewinding the tape is that the backup software doesn't detect this which can lead to overwritten data.

Q again, does anyone know if it's possible to change the behaviour of the DLT drive to not rewind upon a SCSI reset?
David Ruska
Honored Contributor

Re: DLT rewind problems

There are few things that can reset a drive, including bus resets from the host, invalid SCSI command sequences, power glitches, and internal firmware errors (bug checks).

In some cases unexpected rewinds are also caused by application conflicts. This is very common in SAN environments, where multiple hosts have access to a common tape drive. For example, if any application on unix (e.g. make_net_recovery or diskinfo on a tape device file), accesses a device file with the rewind-on-close bit set.

If this is not in a SAN, then I would suggest looking at the logtool output and also viewing the drive's last N events log to see what errors are logged (if any) in the drive. The latter can be done using HP Library & Tape tools on UX or Windows (see www.hp.com/support/tapetools).
I can help you interpret any errors in the drive logs.

Regarding bus problems, ensure that the cable lengths are in-spec, terminators are good, thumbscrews are tight, etc.

Does the problem just happen on one DLT7000 drive, or on more them one?

Lastly, what version of firmware are you using? The DLT7000 standalone drive from HP is on V101.
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