compression on a tape drive with "c" option

[Joe Astrologo]

How do I use compression on an autoloader tape library using the c option on the device (i.e. /dev/rmt/0mnc). Or do I have to create a new device file with compression capabilities.

[rajsri]

If you are using these drives on HPUX box ,
/dev/rmt/cxtxdxBEST is the compressed device, normally this file is linked to /dev/rmt/0m , have a look at /dev/rmt/* files .

[Patrick Wallek]

Rasiri is correct. There typically is not a 'c' device on HP machines. The /dev/rmt/#m is your best choice to get the desired result.

[Dan Hetzel]

Hi Joe,

There is no "c option" in HP-UX.
The BEST device provides automatic compression and is linked automatically to /dev/rmt/?m

Using that one will give you the BEST possible tape capacity.

BEST Regards :7)

Dan

[Suhas_2]

HI,
I agree with what Unix Guru's are saying.
1> On HP you have ?m as the best drive.
2> If you are on SunOS pls try using /dev/rmt/?h
(h for high density), if that is not present pls check in /devices directory, for the below mentioned file

/devices/iommu@f,e0000000/sbus@f,e0001000/espdma@f,400000/esp@f,800000/st@6,?:h

You can make a link of ?h in /dev/rmt dir to above "greek" path. ;-))..

Hope this helps...
Suhas.

[Tom Danzig]

You can verify that /dev/rmt/#m is using compression. Use ls -i on the device files. If the inodes are the same (such as 0m and c4t3d0BEST below are 1005), your using compression.

# ls -i /dev/rmt | sort
1005 0m
1005 c4t3d0BEST
1006 0mb
1006 c4t3d0BESTb
1007 0mn
1007 c4t3d0BESTn

[Jason Morgan_1]

run an, "ioscan -funCtape" without quotes.

this should give you a listing of all the tape drives on your system. it also lists different ways to store your data on the tape.

-jason

[Bill Hassell]

A couple of notes:

ioscan -funC tape

is much faster with k:

ioscan -kfnC tape

The -k option reports what the kernel knows about from memory rather than scanning all the hardware in the system. Unless you connect devices to a running system (not a good idea), the -k option tells you about everything in the system virtually instantly.

Also, no one has mentioned the device file decoder: lssf In the old days of HP-UX, you could use ll, rm, and mknod to manage hardware, but with widely varying (and large scale) hardware, ll should be replaced with lssf to show the details about a device file. And rm should be replaced by rmsf to remove device files, and insf/mksf rather then mknod for making new device files.

The term BEST density means that the driver will enable the highest density possible on the device, whether through recording method or hardware compression, whichever applies.

[Carlos Fernandez Riera]

use lssf to see atributes of your special files:

lssf /dev/rmt/*

and mksf to create a special files with special requeriments:

mksf -H 0/...... -b DDS2C ..... /dev/rmt/drive1_c


see man mksf