Only 12 gig fits on DDS3 with SureStore DAT24

[Bill Hassell]

As mentioned, compression depends on 2 factors: device file and the data itself. For HP-UX, *always* use the lssf command to decode device files. (related commands: insf, not mknod, and rmsf, not rm). The word: BEST density indicates that when the this device file is used, the driver will set the compression option on the drive.

To test compression, use the prealloc command to create a very large (multi-meg) file. It will be extremely compressible (perhaps 10:1 up to 100:1). However, to easily see that the data is compressed, get a copy of the tapeinfo program from:

ftp://contrib:9unsupp8@hprc.external.hp.com/sysadmin/programs/tapeinfo/

[Frank Slootweg]

Which backup utility do you use?

If fbackup, then run it with the "-v" option. That will report how much data fbackup writes to the tape drive, i.e. including fbackup 'overhead'. If that number is slightly over 12GB (the Native Mode (= uncompressed) capacity of a DDS3 tape) (or more), then apparently hardware data compression is working and all is well.

[John Downs_1]

Hi again, I'm using dump and the tape drive is configured to do compression. This is the lssf output of the device file that I am using:

stape card instance 1 SCSI target 1 SCSI LUN 0 at&t no rewind best density available at address 8/16/5.1.0 c1t1d0BESTn

Thanks!
-john

[John Downs_1]

Still no solution. I suspect that I am using the wrong arguments in the dump command. The dump command is : rdump 0udsf 60000 30000 la:/dev/rmt/c1t1d0BESTn filesystem.

I'm using HP dds-3 cartridges C5708a

How do I now or determine the density and length of a tape?

-john

[Vincent Farrugia]

Hello,

On the back of all DDS tapes, there should be 7 holes.

DDS3 tapes have the holes setup as follows:

From left to right:

1st Hole: open
2nd Hole: closed
3rd Hole: open
7th Hole: closed

All DDS3 tapes are 125m long.

HTH,
Vince

[Frank Slootweg]

> How do I now or determine the density and length of a tape?
[for dump(1M)]

dump(1M) and friends are for reel-to-reel magtapes. DDS is totally different, so you have to 'fool' dump(1M) that it is talking to some special magtape drive.

As far as I know, this subject is (still) covered in the "comp.sys.hp.hpux FAQ". You should be able to find this FAQ on Google Groups. Let me know if you can not locate it and I will look for you.

[John Downs_1]

Hi, the tape is as you said. But I'm still not sure if I am giving the correct options on
the dump command line.

I couldn't find comp.sys.hp.hpux. I tried http://www.comp.sys.hp.hpux, comp.sys.hp.hpux with the same results. Can't find server or server is down.

Is google group a different location?

-john