topic Re: tape compress issue in Operating System - HP-UX

tape compress issue

lin.chen — Tue, 22 Jan 2008 15:56:23 GMT

Dear all
I have a problem about data compression using the IBM LTO3 driver inside a tape library on hpux11.31.
when I create a file which is more than 400G by "dd",I try to backup with "/dev/rmt/0mb".
But it seems that there is no compression.

Yes.maybe some file is non compressable,but it seems compress really not work.
How shall I do on hpux?
Regards,Chen Lin

Re: tape compress issue

OldSchool — Tue, 22 Jan 2008 16:05:13 GMT

how are you determining that compression doesn't work?

does the backup fail?

exactly what did you do to:
a) create the file -and-
b) backup the file

what was the output of the backup step that causes you to thing compression doesn't work?

Re: tape compress issue

lin.chen — Tue, 22 Jan 2008 16:09:09 GMT

Dear,
Thanks for your reply?
the tape is 400G(non compress)
I just create a file for 420G,but i can not backup the file completely.
So I suspect the compression is disable on hardware.
Regards,Louis

Re: tape compress issue

lin.chen — Tue, 22 Jan 2008 16:09:20 GMT

Dear,
Thanks for your reply!
the tape is 400G(non compress)
I just create a file for 420G,but i can not backup the file completely.
So I suspect the compression is disable on hardware.
Regards,Louis

Re: tape compress issue

OldSchool — Tue, 22 Jan 2008 16:14:01 GMT

again: "exactly what did you do to:
a) create the file -and-
b) backup the file"

commands used?????

what happens if you use compress or gzip the file to disk?

Re: tape compress issue

lin.chen — Tue, 22 Jan 2008 16:19:48 GMT

#dd if=/dev/zero of=/tmp/test bs=4k count=1100000
#gzip /tmp/test <<
#tar cvf /dev/rmt/0mnb /tmp/test
<<<

Re: tape compress issue

Tim Nelson — Tue, 22 Jan 2008 16:37:05 GMT

#dd if=/dev/zero of=/tmp/test bs=4k count=1100000
#gzip /tmp/test <<
#tar cvf /dev/rmt/0mnb /tmp/test
<<<

you already compressed it with qzip !!! There is nothing for the tape drive to compress.

Re: tape compress issue

lin.chen — Tue, 22 Jan 2008 16:40:14 GMT

Hi Tim,
I did not use the test.gz for backup test,while I used /tmp/test <<

Re: tape compress issue

Tim Nelson — Tue, 22 Jan 2008 16:40:19 GMT

BTW,

Your profile shows that you have only assigned 89 of 305 points to your questions.

Not that you should spend hours assigning old points but this is how we say thanks for the help on this forum.

Re: tape compress issue

OldSchool — Tue, 22 Jan 2008 16:54:47 GMT

I suspect you might have a driver issue. What does "ioscan -nfC tape" report?

also, see this thread regarding driver availablity from IBM on 11v3:
http://forums12.itrc.hp.com/service/forums/questionanswer.do?threadId=1164531&admit=109447627+1201020551093+28353475