On Wednesday 12 February 2003 18:37, John Oliver wrote:
>On Wed, Feb 12, 2003 at 06:05:03PM -0500, Joshua Baker-LePain
wrote:
>> If you want to continue using software compression (let's amanda
>> be more accurate), then turn off compression at your tape drive.
>
>For the life of me, I can't find how to disable hardware
> compression. Drive is a Quantum TH5AA DLT 4000. I found the
> Product Manual on Quantum's site, and it mentions that you *can*
> disable compression, but neglects to say how. Nothing I can find
> does :-(
Generally speaking, the "Product Manual", or Owners Manual is
written for the Joe Sixpacks and sales dweebs and is generally
couched in terms only a lawyer would understand because it was
written by lawyers to protect the companies butt.
What you need is the Technical Manual. And I'd suspect thats an
extra cost item today, but it will be found to be very valuable in
terms of setting up a good backup formula for your site(s).
You may be able to enquire at Quantum via email as to how to do this
if you can find an email link on a support page.
Using the drives hardware compression is, as other have pointed out
already, a very slippery slope because then amanda never knows how
much tape she has left. With the hardware compression off, and
using that "no compression" capacity or a few percent less, amanda,
who counts bytes actually fed up the cable to the drive, has a very
good idea of the tapes remaining capacity. Software compression
can often beat the hardware, in some cases by a lot. My average
compression ratio here is to about 38% of original in any one run
and half of my DLE's do not use compression because those DLE's
point to directories full of .gz, .bz2, and .rpm's. Some DLE's
compress to less than 10% of original size so the average still
beats the hardware method quite handily...
--
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz 512M
99.23% setiathome rank, not too shabby for a WV hillbilly
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