I haven't encountered that. I thought that the compression algorithms
were standardized for particular tape formats. Typically, the originator
of a tape format is the primary manufacturer and other vendors repackage
mechanisms with their own labeling and other components. So, e.g., a Sun
or Dell DAT drive would be the same tape mechanism, which they bought in
bulk and repacked.
For amanda, a principle issue is planning. Hardware compression makes it
more difficult to plan ahead, because amanda doesn't know how
compressible the data is or how much space it actually took up on the
tape. With experience, it can figure it out statistically for a
particular DLE, but it can't really know. This might not be an issue
with other software which doesn't plan. Such software just does what you
tell it and simply asks for another tape when it runs off the end. It
becomes your responsibility to plan and to respond to shifts in disk
usage over time, and that's one of the major advantages of amanda.
---------------
Chris Hoogendyk
-
O__ ---- Systems Administrator
c/ /'_ --- Biology & Geology Departments
(*) \(*) -- 140 Morrill Science Center
~~~~~~~~~~ - University of Massachusetts, Amherst
<hoogendyk AT bio.umass DOT edu>
---------------
Erdös 4
Donofrio, Lewis wrote:
> This is my first post here - I thought people should never use tape hw
> compression because each vendor implements their own compression
> protocols. Say you need to restore files from a different tape host and
> if your not using the exact same hw vendor then you might have an
> *issue* or two?
>
> --and keep in mind this logic that is in my head is for "other" backup
> programs I do not know how Amanda deals with (or even cares) about low
> level mt/st stuff.
>
>
>> -----Original Message-----
>> From: owner-amanda-users AT amanda DOT org [mailto:owner-amanda-
>> users AT amanda DOT org] On Behalf Of Olivier Nicole
>> Sent: Tuesday, May 01, 2007 11:02 PM
>> To: dist-list AT LEXUM.UMontreal DOT CA
>> Cc: amanda-users AT amanda DOT org
>> Subject: Re: activate HW compression
>>
>> Hi,
>>
>>
>>> How can I enable Hw compression ? do I have to do it for each tape
>>>
> ?
>
>>> What if A reboot the server ?
>>>
>> Yes you have to activate it for each tape, and on the safe side, I
>> would activate it before each amanda run, so make it part of the cron
>> that runs amanda dumps.
>>
>> Olivier
>>
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