Date: Mon, 18 Feb 2002 14:05:29 +1100
From: Timothy Shimmin <tes@boing.melbourne.sgi.com>
To: Esger Abbink <e.abbink@chello.nl>
Cc: linux-xfs@oss.sgi.com
Subject: Re: xfsdump & compression? (was: Re: xfsdump aborts after assertion  failure)
Message-ID: <20020218140529.G2733461@boing.melbourne.sgi.com>
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In-Reply-To: <001401c1b81e$e29accd0$6f07bbd4@burner>; from e.abbink@chello.nl on Mon, Feb 18, 2002 at 02:52:13AM +0100
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my 2 cents...

On Mon, Feb 18, 2002 at 02:52:13AM +0100, Esger Abbink wrote:
> So, as i understand it there is no "safe" compression aside from hardware
> compression while using xfsdump.
> 
I think "safe" is a subjective thing here.
I think it is more a question of "safer".
Option 2 may still be considered viable for some.
If one has tape errors then things probably aren't going to be pretty ;-)
If one uses the tape strategy (e.g. by "-f /dev/st0" as opposed
to stdout), and something happens to the tape such that we
get an error on reading on restore - then it allows us to
move onto the next media file in the dump. But this is only
of some comfort -> the rest of the data in the corrupt media
file is gone, we may only have one media file, there may be
other errors in other media files.


(Hmmm.. and if one was desperate to restore as much as possible,
 and one had a tape error, then having gzip'ed data would
 probably make things pretty tricky to recover stuff.)

--Tim

> as the data volume is quite big, i really need compression. recommandations
> for backup software anyone?
> 
> ----- Original Message -----
> From: <ivanr@sgi.com>
> To: "Bernhard R. Erdmann" <be@berdmann.de>
> Cc: "Esger Abbink" <e.abbink@chello.nl>; <linux-xfs@oss.sgi.com>
> Sent: Monday, February 18, 2002 2:22 AM
> Subject: Re: xfsdump & compression? (was: Re: xfsdump aborts after assertion
> failure)
> 
> 
> > On Sat, 16 Feb 2002, Bernhard R. Erdmann wrote:
> >
> > > > how do i get xfsdump to compress stuff?
> >
> > xfsdump does not compress stuff.
> >
> > > 1. use hardware compression
> > > 2. xfsdump -J -F - / | gzip | dd of=$TAPE bs=32k
> >
> > Option 2 will nullify all of xfsdump's fault tolerance features when
> > writing to tape.  In other words, if there's a tape error or you hit the
> > end of tape, xfsdump can't recover.
> >
> > I understand of course that this might be fine for some, but many sites
> > don't like to take chances with their backups.  Just thought I'd mention
> > this in case it was an issue.
> >
> > Ivan
> >
> > --
> > Ivan Rayner
> > ivanr@sgi.com
> >
> 
>