LVM question. Missing about 11GB of Space..

[Michael D. Setzer II]

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On 29 Oct 2005 at 18:14, Alexander Dalloz wrote:

From:	Alexander Dalloz <ad+lists at uni-x.org>
To:	For users of Fedora Core releases <fedora-list at redhat.com>
Date sent:	Sat, 29 Oct 2005 18:14:47 +0200
Subject:	Re: LVM question. Missing about 11GB of Space..
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> Am Sa, den 29.10.2005 schrieb Michael D. Setzer II um 17:19:
> 
> > In doing a backup of a 250GB drive, I was surprised to have a 
> > compressed image that was larger than the used space. In the past, 
> > I've compressed an 80GB drive with 3 OS's, and get a 14GB image. 
> > This is a 250GB drive with only 1 OS, and it is producing an 18GB 
> > image. All free space is zeroed out.  In doing some research, it 
> > appears that about 5% of the LVM partition is being used in some 
> > fashion that I am not aware of. 
> > 
> > The drive shows the volume size as 229GB with 12GB uses, and 
> > 206GB Free. That leaves about 11 - 12 GB missing. 
> > 
> > Whatever is in this 5% of the drive doesn't appear to compress very 
> > well with either lzop or gzip. With lzop the image is about 18GB and 
> > 16GB with gzip, but lzop only takes about 2 hours, whereas gzip 
> > takes about 3 1/2 hours. The image only seems to be runing fine 
> > until it gets to the end were this 5% seems to be, and it grows 
> > rapidly. 
> > 
> > Any info on what this 5% is. I'm using g4l, which uses dd to copy the 
> > raw partition information, and uses lzop or gzip compression. I was 
> > thinking it might be some kind of swap, but why it would be 5% of 
> > the disk size, as compared to the amount of ram. 
> 
> This has nothing to do with LVM. Please see "man mkfs.ext{3,2}" -> -m
> reserved-blocks-percentage
> 
> "Specify  the  percentage  of the filesystem blocks reserved for the
> super-user.  This value defaults to 5%."

Thanks, that explains why it was setup that way, but it was done 
automatically with the installation of the Fedora, so can it be 
changed after the fact?? Or is there a way to atleast blank out the 
reserved area with nulls. I zero out all the free space, but it doesn't 
have access to that area. 

I do now that the 250GB drive is 251,000,193,024 bytes, and 
produces the /dev/hda1 as 104,391  (1 to 13) and /dev/hda2 as 
245,007,315 (14 - 30515).

If I can zero out this area, it should reduce the size of the g4l 
images, and speed up the restore process. With the 80MB drives, it 
is less than 2GB, but with the 5% of the 250GB drive is is larger.

Thanks again.


> 
> Alexander
> 
> 
> -- 
> Alexander Dalloz | Enger, Germany | GPG http://pgp.mit.edu 0xB366A773
> legal statement: http://www.uni-x.org/legal.html
> Fedora Core 2 GNU/Linux on Athlon with kernel 2.6.11-1.35_FC2smp 
> Serendipity 18:12:02 up 15:12, 16 users, 0.15, 0.26, 0.15 
> 


+----------------------------------------------------------+
  Michael D. Setzer II -  Computer Science Instructor      
  Guam Community College  Computer Center                  
  mailto:mikes at kuentos.guam.net                            
  mailto:msetzerii at gmail.com
  http://www.guam.net/home/mikes
  Guam - Where America's Day Begins                        
+----------------------------------------------------------+

http://setiathome.berkeley.edu
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