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Re: [Xen-users] Understanding sparse-files

  • To: "John Haxby" <john.haxby@xxxxxxxxxx>
  • From: "Todd Deshane" <deshantm@xxxxxxxxx>
  • Date: Tue, 16 Dec 2008 16:13:49 -0500
  • Cc: "Rustedt, Florian" <Florian.Rustedt@xxxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Tue, 16 Dec 2008 13:15:13 -0800
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  • List-id: Xen user discussion <xen-users.lists.xensource.com>

> There are some problems with sparse files: the compress beautfully (gzip
> reports 99.9%) but it takes a while to read the empty space and when you
> uncompress the file you discover that it now actually occupies disk space:
> there's no good way to distinguish between an unallocated block and a block
> full of zeroes.   This also means that you need to be careful how you back
> these files up: you need something a little cleverer than gzip.

You can use tar with the S (sparse) option here.
Also I think that you should be able to use cp
with a --sparse option as well.

To distinguish, using the du command helps.


Todd Deshane

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