linux tar doesn't backup in compression mode

[richard_263]

Hello
In first excuse me because i don't speak english very well (i am french)
i installed linux fedora core1 on 2 HP proliant ML350 G3 ; each computer has a tape drive :
COMPAQ (SONY) SDT 10000 and HP C5683A
on theses computers, when i make a tar cvf /dev/st0 /myrep_tosave, i cannot save the same volume of data as it's written on the cartridge because it's written compressed capacity.
So i think that the hard compression is not active ; i try to change the jumpers on the SDT 10000 but i get the same trouble
how can resolve this problem ?
thanks

[JohnWRuffo]

Richard:

You should download the Library and tape Tools for linux to diagnose if the drive has a hardware compression set or not. Click here to get the latest L&TT: ( ftp://ftp.hp.com/pub/softlib/software3/COL1977/co-18251-1/hp_ltt34sr1a_linux_64.tar )

Vous devez telecharger les Outils de Bibliothèque et bande pour Linux pour diagnostiquer si l'unite a une serie de compression de materiel ou pas. Cliqueter ici pour obtenir le dernier L&TT: ( ftp://ftp.hp.com/pub/softlib/software3/COL1977/co-18251-1/hp_ltt34sr1a_linux_64.tar )

Vous etes anglais etait bon, mon francais est mauvais. Bonne chanc

[richard_265]

Thanks for your answer

I've downloaded, installed and run this software ; but i don't understand what it makes ! i tried a few things and my tape seems to be right (safe ?)

strangly, the software see a tape on /dev/sg0 ; (i always use /dev/st0).

If i try to use /dev/sg0 (with tar or mt -f /dev/sg0 status), it doesn't work

about the files that i want to save, there are a lot of tif files and may be other compressed files (like tar.gz) and so the hardware compression do nothing for this kind of files ?

now, i would want to know how many Gb i can store on a cartridge where it's written, about capacity, "24 gb compressed"

[JohnWRuffo]

The L&TT can give you the settings (that it can read) from the drive.
when you run the program ./hp_ltt you get past the splash screen you can "select 1" or "select 2" to get each of your drives. If you load a tape into the drive before you run hp_ltt it will read the tape and give you the capacity. It should also tell you if the drive has compression.

You can do some "tests" againts the drive to check if compression is on or a valid setting. If you have trouble, generate a trouble ticket from the program and send off the e-mail to the LTT team. They can give you some good answers too.

[JohnWRuffo]

Well... to be honest, you really cannot compress already compressed files and .tif files are fairly well compressed anyway so, no, you will not get much if any compression on your volumes with these types of files. You will have to span tapes if you cannot fit the entire filesystem on one tape.

[Roberto Polli]

1) did you try if tape works using
# tar tvf /dev/st0
2) did you try do save data using
# tar cfz /dev/st0 /dir/to/save

Peace, R>

[richard_265]

yes, i try tar tvf /dev/st0 and tar cvfz /dev/st0 rep_to_save ; and they works but my problem is to know how many GB i can save on one cartridge...

[JohnWRuffo]

Richard:

Does the media you are using not have the capacity labled on the cassette? ( http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?locale=en_US&objectID=lpg50116&locale=en_US&taskId=101&prodSeriesId=63890&prodTypeId=12169) if not, put one of the tapes in the drive, let it load and then run the LTT. Select the drive you wish to see the capacity of and once it has read the drive parameters and tape header, the screen should show the capacity of the tape you are using.

[Roberto Polli]

use

dd if=/dev/zero of=/dev/st0 bs=1024

The output gives you how many 1024 blocks you can write on the tape.
It's already been answered.

Look at http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=425728
or search on these forums

Peace, R.