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why not compress and then dd to tape

backup?

From: Tony Lawrence <tony@pcunix.com>
Subject: Re: Two questions reated to tape
Date: Wed, 05 Feb 2003 11:12:07 GMT

news@roaima.freeserve.co.uk wrote:
> Tony Lawrence <tony@pcunix.com> wrote:
> 
>>Writing to a tape with dd is in fact common enough that it's often used 
>>in faqs as an example of what NOT to do (tar to a file, compress that, 
>>dd to tape).
> 
> 
> To which FAQs are you referring, and what's wrong with a snippet like
> this anyway?
> 
>     cd / && find . {some args} |
>    egrep {some filter} |
>    cpio -ocB |
>    gzip |
>    dd ibs=1K obs=1024K of=$TAPE

What's wrong is that you've compressed the the whole archive and then 
written out to a media that can have bit errors.  If there is a problem, 
you lose the entire archive.  That's the warning that you'll find in the 
aforementioned faqs.  There's also the obvious limitation that you can't 
grab a particular file from that tape.

Not that people don't do this :-).  If you understand the risks and 
limitations and still want to do it, go right ahead.




-- 
Tony Lawrence
Free SCO, Mac OS X and  Linux Skills Tests: 
http://aplawrence.com/skillstest.html

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