Re: software compression out

From: John Kuiper (jkuiper_at_thematec.nl)
Date: 09/01/03 

Date: Mon, 01 Sep 2003 11:37:34 +0200

I did some tests for myself.
The default backup program is tar. Normally the command for using backup
is 'tar cf /dev/rStp0 <files>' or 'tar c8 <files> (witch 8 stands for
/dev/rct0 in /etc/default/tar). In the /etc/default/tar the settings are
set for the tape; archive8 /dev/rct0 20 0 y.
If tape is set to n, then tar will see the tapedevice as a harddisk and
is not using blocksizes. The files are put directly to the tape without
software compression, but hardware compressing.
If tape is still y but the volumesize is set to 24000000 (for example),
the files are put directly to the tape without software compression, but
only using hardware comression.
On any other way (like tar cf /dev/rStp0) the files are first to be
compressed and then put on the tape drive.

Tell me if I have it wrong?

John Kuiper

Bob Bailin wrote:
> "John Kuiper" <jkuiper@thematec.nl> wrote in message
> news:bil3kr$41l$1@reader10.wxs.nl...
>
>>Hello,
>>
>>I have a SDT-9000 tapedrive built in my sco 5.5 server.
>>It works, but very slow.
>>I found out that both software compression and hardware compression are
>>enabled. The command tape -s -a -0 setcomp should disable the software
>>compression but gives the error:
>>"tape: unable to do 'setcomp' command on '/dev/xct0' : Invalid argument"
>>
>>Is there another way to turn off the software compression.
>
>
> The setcomp option to the tape command controls hardware, not software
> compression. Your (unspecified) tape backup program controls software
> compression, and should be turned off if you're using a device with
> hardware compression.
>
> The SDT-9000 works much more slowly with DDS-1 and DDS-2 tapes
> (60,90,120m) than with DDS-3 tapes (125m).
>
> Bob
>
>

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