topic Re: tape device in Operating System - HP-UX

tape device

Jeff Hagstrom — Thu, 15 May 2008 11:32:13 GMT

I have an RP7410 and we have DDS 3 tape drive. The tapes are 12/25. How do use the 25 gig side. My databases and files are just over 15 gig and I want it all to sit on one tape. Right now I'm taring the tape:
tar -cvf /dev/rmt/1m (directories)

Re: tape device

James R. Ferguson — Thu, 15 May 2008 11:38:53 GMT

Hi Jeff:

The "25" is what you *might* get with maximum compression. The actual compression you achieve will be data-dependent.

To see if your tape drive uses the best compression available, do:

# lssf /dev/rmt/

You will probably see something like "best density available".

Regards!

...JRF...

Re: tape device

Torsten. — Thu, 15 May 2008 11:40:55 GMT

Thanks to the marketing (not only HP!) all the tapes have nice names like 12/24GB.

But it means all the times 12 GB native and 24 GB compressed with an ideal rate of 1:2.

If your data is not compressable that way and you get only - let's say 1:1.5 - you can store only 18GB on that tape.

If your data is already compressed and you get only 1:1 - you can only store 12 GB on the tape.
That's it.

Be aware of all the different device files of your tape!

Re: tape device

Jeff Hagstrom — Thu, 15 May 2008 11:47:52 GMT

# lssf /dev/rmt/1m
stape card instance 7 SCSI target 3 SCSI LUN 0 at&t best density available at ad
dress 1/0/8/0/0.3.0 /dev/rmt/1m
So this is telling me that the best device to use is 1m?

Re: tape device

James R. Ferguson — Thu, 15 May 2008 11:50:10 GMT

Hi (again) Jeff:

> So this is telling me that the best device to use is 1m?

In a manner of speaking, yes. It is saying that you will get the "best density available" when using this device. There may be other equally good devices are your server.

Regards!

...JRF...