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Date:      Mon, 30 Oct 2000 01:40:30 -0600 (CST)
From:      Ryan Thompson <ryan@sasknow.com>
To:        Leif Neland <leif@neland.dk>
Cc:        Matt Dillon <dillon@earth.backplane.com>, freebsd-hackers@FreeBSD.ORG
Subject:   Re: Filesystem holes
Message-ID:  <Pine.BSF.4.21.0010300109440.86769-100000@ren.sasknow.com>
In-Reply-To: <01a801c04236$ed0a0d20$0e00a8c0@neland.dk>

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Leif Neland wrote to Ryan Thompson and Matt Dillon:

> 
> What will happen, if somebody (possibly you, as mahordomo says), tries to
> make a backup of that file.

Make sure to use a program that can cope ;-)


> Will the copy also be with holes, or would that file suddenly use all 96GB?
> It will at least do so, if one does cat file>file.bak
> Probably tar will do the same.

Actually, tar will handle holes elegantly (this I have tested), with the
--sparse option.  Older versions would not.  cat and other similar
"filters" are naive, as they simply block I/O.

Backing up with tar and/or a filesystem dump would be just as effective as
with any other storage strategy.

cat file > file.bak on even a 2GB file is probably not something that
would be popular, anyway.

> I'd be afraid to create something which could easily blow up by having
> normal operations applied to it.

That's a valid concern.  That's the biggest drawback I see to the overall
strategy... But, specialized problems sometimes encourage specialized
solutions.

> 
> Leif
> 

-- 
  Ryan Thompson <ryan@sasknow.com>
  Network Administrator, Accounts
  Phone: +1 (306) 664-1161

  SaskNow Technologies     http://www.sasknow.com
  #106-380 3120 8th St E   Saskatoon, SK  S7H 0W2



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