On Mon, Apr 02, 2007 at 03:24:17PM -0400, Freels, James D. wrote:
> I have a new set of X23 tapes from Exabyte (now Tandberg) that I want to
> make sure I get the most out of with my AMANDA backup system.  The tapes
> are rated at 80/160 GB (uncompressed/compressed) for my VXA-2 drive.  A
> few questions:
> 
> 1) compresstion
> 
> I read where hardware compression in the tape drive should not be used
> with AMANDA.  If you want compression, use the computer software (gzip)
> to do this in the AMANDA configuration.  Is this still true ?

Lots of reasons on both sides to choose one or the other.  I'd guess more
than half of amanda installations use software compression.  But make sure
you don't attempt to use both.

> 
> 2) block size
> 
> I have read mixed advice on the blocking size.  It seems that a variable
> blocking size (mt setblk 0) is the best, but I have also seen where a
> large fixed block size like 32768 is appropriate.  I tried this fixed
> block size and it seem to fail my system, so I changed it back to
> variable.  What is the advice here ?

By default amanda will write 32KB blocks.  So variable is fine as is fixed
at 32KB.  If you experience tape performance problems consider having amanda
use a larger block size (requires a recompiliation of amanda).

> 
> 3) tape density
> 
> The VXA-2 manual and the output from "mt status" indicate that a tape
> density parameter of 0x81 is being used by this tape drive.  However,
> the output from "mt densities" shows 0x81 as "DLT 15 GB compressed".  I
> want the setting that will give me 80GB on the tape.  What would that
> be ?

Check the tape's capacity with amtapetype -e <estimated size>.
Should take about 7 hours.

> 
> 4) stinit.def file
> 
> I am using the debian mt-st package.  The drive is presently initialized
> with a /etc/stinit.def file shown below.  How should I change this (if
> any) ?
>         
>         manufacturer = "EXABYTE" model = "VXA-2" revision = "2100" {
>         scsi2logical=1
>         density=0x81
>         can-bsr=1
>         can-partitions=1
>         auto-lock=1
>         async-writes=1
>         read-ahead=1
>         buffering=1
>         mode1 blocksize=0 compression=0
>         mode2 blocksize=0 compression=1
>         mode3 blocksize=32768 compression=0
>         mode4 blocksize=32768 compression=1
>         }
>         

? Mine are not so specific.

-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
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