On Monday 02 June 2003 15:02, Brendon Colby wrote:
>On Monday 02 June 2003 10:40, Gene Heskett wrote:
>> If you then had to recover, you would need only the last
>> 'dumpcycle' tapes. Note that I didn't say 7 though, because you
>> might be running a 5 day a week runspercycle, so that would be
>> only the last 5 tapes.
>
>Ok. Thanks - this just clicked for me.
:)
>> One would use the capacity the makers says it has when the
>> compression is turned off. Software is the prefered method, for 2
>> reasons.
>
>My tapes say 40* - 80* GB (* = compressed). This is a DLT 8000
> drive. This means that I have a 20GB capacity uncompressed? (Just
> to clarify.) The 40 - 80 GB means I can get between 2 to 4 times
> the storage with compression on?
No, that would be somewhere near 40GB without any hardware
compression, and 80 GB with it. These are round figures of course,
subject to the usual propaganda discount. By the time you make room
for filemarks and such, that 40 might be less than 39 in the real
world.
>> 1. gzip can normally outcompress the hardware compressors in most
>> drives. Night before last, the disklist and dumpcycle positioning
>> was such that I put something over 10 gigs on a 4 gig DDS2 tape.
>> Of course I don't do that every nite :)
>>
>> 2. amanda counts bytes sent to the tape. If the hardware
>> compression is on, then amanda has no clear view of the tapes
>> capacity and will happily write till it hits EOT if you are
>> feeding it already compressed files, like a whole dir full of
>> rpm's or tar.bz2's, which will probably grow some in the
>> compressor. So you have to set the tapetype to something less
>> than the makers propaganda claims & then (optionally, I've not
>> been able to prove its effective) sacrifice a chicken. If its
>> turned off, then amanda has a pretty good view of what the tape
>> can hold and will fill it reliably to 95+% without ever hitting
>> the tapes EOT.
>>
>> There is an amtapetype utility in the distribution that can test
>> that for you. But start it early in the day, it takes a while to
>> run.
>
>I have already decided to use software compression (esp. for reason
> #2 above). I will have to compile the distro from the Amanda site
> as the Debian packages must not contain the amtapetype utility.
Get the latest 2.4.4 snapshot from that link near the botton of the
amanda.org page. And if you are going to build ti from scratch,
commit the configuration options into a script, such as the one I
bore this list with by reposting from time to time, the last time s/b
within this past week IIRC. No, its not carved in stone. The
emphasis on useing the script is so that if you decide to upgrade to
the latest snapshot, you are always using the same set of options and
the upgrade is a 4 minute job with no surprises on a midrange piece
of iron.
>Thanks for everyone's help.
--
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz 512M
99.26% setiathome rank, not too shabby for a WV hillbilly
Yahoo.com attornies please note, additions to this message
by Gene Heskett are:
Copyright 2003 by Maurice Eugene Heskett, all rights reserved.
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