Trying to use dd to dump to tape drive 7980s in uncompressed format

[George Doller]

Hi, This is my first time posting a question, so please bare with me. I am trying to use the dd command to write to a 7980s tape drive in uncompressed format and it always seems to be compressed. The tape goes to the gov't and comes back saying, the tape begins with invalid records, use uncompression. here is the dd command I used.
dd if=(input file) of=/dev/rmt/1m bs=6900 conv=block cbs=276 conv=ebcdic

thanks for any input

[Victor BERRIDGE]

Hi,
I dont see any thing wrong with your command:
rmt/0m for reel tape drive would write at 1600 bpi where as 0h would be 6250, only I have never used your type of drive, woulndt it be a HP7980/XC ? This model has a special data compression capability, I would suggest that you find the manuals of your drive and see how to deacitvate the data compression facility, but as said befor I heard of this model fes years ago but never seen one...

Good luck

All the best

Victor

[Andy Monks · Accepted solution]

check the device file your using.

do an 'lssf /dev/rmt/1m'. If it says 'BEST' then it will use compression.

Create an non-compression device file (I'd use sam) and then use that.

[Victor BERRIDGE]

Hi Andy,
Youre right, Ive forgot I had to customize my devices when passed to HPUX10.2 for reel tapes 2-3 years ago...

All the best
Victor

[George Doller]

The answer of adding a new device file was the answer.
Thank you very much

[Joseph A Benaiah_1]

George,

You can create a DDS1 device file which does not compress data when writin go tape by running:

mksf -C tape -b DDS1

You will then have extra tape device files that have the format:

/dev/rmt/c_t_d_DDS1.

Regards,

Joseph.

[paul courry]

With regard to compression on the 7980/XC, pressing the ENTER button (last button, upper right) will display whether compression is on or off. Pressing NEXT then ENTER will toggle compression. (God, have I been around that long?)