DAT drive deveice files - which to use ?

[Simon R Wootton]

I have an L class server with it's default DAT drive as installed on delivery. Which file do I use in the /dev/rmt directory - pls help !!

[suranji]

are there any device files in that /dev/rmt/ directory ? If not see the DAT drive is claimed by using

ioscan -funC tape

then use insf or mksf with hardware path specified in ioscan output to create device files.

We use use 0m or 1m files as device files for tape backups.

good luck
-suranji

[Magdi KAMAL]

Hi,

Check with the following command to see which one is used by the hp-ux kernel :

ioscan -fnkCtape

Magdi

[melvyn burnard]

If it is default, then use /dev/rmt/0m

use ioscan to check the hardware path, ioscan -funCtape will give you the device files, and lssf /dev/rmt/0m should show you the correlation between the device file and the hardware path.

[Patrick Wallek]

I would use either /dev/rmt/0m or /dev/rmt/0mn the difference between the 2 is:

0m will rewind the tape after it finishes whatever it is doing.

0mn will NOT rewind the tape after it finished. This is useful if you want to put more than one tar, or similar, archive on the tape.

[Harinath N]

Hi Simon,

First do an "ioscan -fnC tape" and check as whether the drive had got sensed, if so and also if the S/W state is CLAIMED, you can use the drive with the device file which you are getting in the ioscan output.
(Normally /dev/rmt/0m)

Eg:

#ioscan -fnC tape
Class I H/W Path Driver S/W State H/W Type Description
======================================================================
tape 0 10/2/2/0.3.0 stape CLAIMED DEVICE QUANTUM DLT7000
/dev/rmt/0m /dev/rmt/c5t3d0BEST
/dev/rmt/0mb /dev/rmt/c5t3d0BESTb
/dev/rmt/0mn /dev/rmt/c5t3d0BESTn
/dev/rmt/0mnb /dev/rmt/c5t3d0BESTnb


Regards,
N.Harinath.

[Dave Wherry]

I had been using the 0m, 1m, etc... device files for my different drives. When I took the OmniBack class back in March the instructor told us to use the device files with "BEST" in the name. It is simply the best choice.

[David Navarro]

Hi,
I think in 10.X and 11.X device /dev/rmt/0m, 1m , etc is the best option for each one. In 9.x /dev/rmt/0m wasn't the best option.

[Bill Hassell · Accepted solution]

A couple of pointers about taoe device files:

-The 'best' choice is usually the best choice but is usually identical to 0m and we all prefer less typing. The important thing to remember is: use lssf in the /dev directory. This command is often unknown and it decodes everything about a device file. The BEST name means that the driver will negotiate with the tape drive for highest performance (typically means hardware compression).

-The default device files are all AT&T behavior which is best described as: bizarre. The reason is that the tape will be respoitioned when closed in the middle of a file. For instance, position a tape to the middle of a file using mt fsf 2 using the no-rewind device file. Now read two records from the same no-rewind device file. This should leave the tape at the start of record 3, so read again. Oops, we are now at record 1 of the next file, not record 3 of the current file.

The AT&T rules are to always position past the EOF mark of the curent file at close. If you want true tape positioning behavior, use the Berkeley device files, specifically no-rewind Berkeley. Read more about Berkeley files in the mt(1) and mt(7) man pages. (hint: man 1 mt, and man 7 mt)