From: Maciej Marcin Piechotka <uzytkownik2@gmail.com>
To: Li Zefan <lizf@cn.fujitsu.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: Inefficient storing of ISO images with compress=lzo
Date: Tue, 20 Sep 2011 01:06:17 +0200 [thread overview]
Message-ID: <1316473579.31049.2.camel@picard> (raw)
In-Reply-To: <4E76AEB9.4080109@cn.fujitsu.com>
On Mon, 2011-09-19 at 10:53 +0800, Li Zefan wrote:
> Maciej Marcin Piechotka wrote:
> > I've noticed that:
> >
> > - with x86-64 Fedora 15 DVD install images:
> > - du -sh <ROOT VOLUME> was 36 GB
> > - btrfs df | grep -i data have shown over 40 GB used
> > - without
> > - du -sh <ROOT VOLUME> is 34 GB
> > - btrfs df | grep -i data have shown less then 34 GB used
> >
> > It seems that iso files are considered compressable while they may not be (and penalty is severe - 3x).
> >
>
> With compress option specified, btrfs will try to compress the file, at most
> 128K at one time, and if the compressed result is not smaller, the file will
> be marked as uncompressable.
>
> I just tried with Fedora-14-i386-DVD.iso, and the first 896K is compressed,
> with a compress ratio about 71.7%, and the remaining data is not compressed.
>
> --
> Li Zefan
Just a question from person who don't know how btrfs operates - what if
the beginning of file is well compressable and the rest is not?
In any case the compression was my uneducated guess where is missing
4GB.
Regards
next prev parent reply other threads:[~2011-09-19 23:06 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-18 23:32 Inefficient storing of ISO images with compress=lzo Maciej Marcin Piechotka
2011-09-19 2:53 ` Li Zefan
2011-09-19 3:13 ` Li Zefan
2011-09-19 23:06 ` Maciej Marcin Piechotka [this message]
2011-09-20 2:19 ` Li Zefan
2011-09-20 14:29 ` David Sterba
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