Can’t read DDS3 tape – tar: tape read error

[angelshark]

Hello,

I’m having trouble reading a DDS3 tape (DAT24) on systems other than its own. This tape comes from a HP 9000 server and it does read well locally but on other HP 9000 or Sun servers I get a tar: tape read error and the cleaning led on the tape drive starts to blink. The tape drives on the other systems are brand new and I already cleaned them so it’s not a cleaning problem. I also tried tar with different block sizes but it didn’t change anything. What could this be?

All your comments and suggestions are welcome.

Thanks for help.

 

[dblair]

are the other DAT decks DDS3 compatible ??
have a look at the pax command (man pax).

 

[angelshark]

Yes, all other DAT decks are DDS3.

I've tried the pax command (pax -r -f /dev/rmt/0m) but the behavior is similar:
pax: [offset 0]: I/O error
pax: Unable to determine archive type.

I wonder what's wrong. Maybe the tape drives need calibration? If so, how do we do that?

Thanks again.

 

[dblair]

no calibration required.
Post the command used to write the tape please..

 

[angelshark]

The command used to write the tape was :

tar cvf /dev/rmt/0m /directory

 

[dblair]

is that 0m or 0n ?
try an mt -ftape_device rewind on the restore server.

Can you test it like this.
On backup server -
insert tape.
mt -f /dec/rmt/0 status
mt -f /dev/rmt/0 rewind
cd /tmp (eg)
tar -cvf /dev/rmt/0 .
eject tape

into restore box.
mt -f /dev/rmt/status
mt -f /dev/rmt/0 rewind
mkdir something
cd something
tar -xvf /dev/rmt/0

let me know how this goes..

 

[guggach]

a remarque:

never save a file ABSOLUT
tar cvf /dev/rmt/0m /directory IS WRONG !!!
tar cvf /dev/rmt/0m ./directory
do you see the difference?
this not your problem, just a tip, taring
absolute path give you a lot of problems.

which tar are|did you using: sun-tar, g-tar, x-tar?

guggach

 

[angelshark]

dblair, I did your test and it works. But I still can't read the old backup tapes on the restore server. They read correctly on the backup server.

guggach, thanks for your tip, I will have to change the backup script to use relative paths instead of absolute.

 

[guggach]

why not dd


guggach

 

[angelshark]

Concluding:

I can not read the contents of this tape anywhere else but in the tape drive that wrote it.

I’ve tried all tools (tar, pax, dd). None of them worked.

Could it be that the tape drive’s head is aligned in a certain way that it writes to tapes in a particular way?

I’m thinking about replacing the tape drive with a new drive. In this way the backup and restore servers will have identically new tape drives.

What do you guys think about it?

Thanks for all your posts.

 

[dblair]

Is it the older backups that you are trying to restore ?
What type of DDS tape are they ? and are you sure of the command used to create these backup tapes ?
If they are DDS2 tapes (for example) then try restoring them on an older tape device.
Or give up and use ftp/nfs to get the files of the tape and onto the other server(s).

Regards..

 

[angelshark]

I'm trying to restore the older backups.

The tapes are DDS-3.

Yes, I am sure of the command used to create these tapes.

I prefer not to use ftp/nfs to get the files because they are an Oracle database.

Thanks again.