Ext3 users - May 2005 - [Q] Where does all the space go?

I created a filesystem as follows:

mke2fs -j -O dir_index -O sparse_super -T largefile /dev/drbd/6

Here's the the output from df

Filesystem            Size  Used Avail Use%
/dev/drbd/6           475G   33M  452G   1%

It seems that ext3 has taken 23 GB, which is about 5% of the total 
disk size, for itself. Is that right?

If that is, indeed, the case, why does df just list 33M as being used?
-- 

Maurice Volaski, mvolaski at aecom.yu.edu
Computing Support, Rose F. Kennedy Center
Albert Einstein College of Medicine of Yeshiva University

Investigate the -m option of mkfs.ext2/3 or tune2fs.
The default is 5%.

Maurice Volaski wrote:
> I created a filesystem as follows:
> 
> mke2fs -j -O dir_index -O sparse_super -T largefile /dev/drbd/6
> 
> Here's the the output from df
> 
> Filesystem            Size  Used Avail Use%
> /dev/drbd/6           475G   33M  452G   1%
> 
> It seems that ext3 has taken 23 GB, which is about 5% of the total disk 
> size, for itself. Is that right?
> 
> If that is, indeed, the case, why does df just list 33M as being used?

On Thu, 19 May 2005, Maurice Volaski wrote:
> mke2fs -j -O dir_index -O sparse_super -T largefile /dev/drbd/6
>
> Filesystem            Size  Used Avail Use%
> /dev/drbd/6           475G   33M  452G   1%
>
> It seems that ext3 has taken 23 GB, which is about 5% of the total disk
size,
> for itself. Is that right?
It's not reserved for the filesystem, but rather for root.  Read about 
the -m option in the manpage to adjust that 5%.
> If that is, indeed, the case, why does df just list 33M as being used?
I think the 33M is the space used by the journal, or the filesystem 
itself.

Damian Menscher
-- 
-=#| Physics Grad Student & SysAdmin @ U Illinois Urbana-Champaign |#=-
-=#| 488 LLP, 1110 W. Green St, Urbana, IL 61801 Ofc:(217)333-0038 |#=-
-=#| 4602 Beckman, VMIL/MS, Imaging Technology Group:(217)244-3074 |#=-
-=#| <menscher at uiuc.edu> www.uiuc.edu/~menscher/ Fax:(217)333-9819 |#=-
-=#| The above opinions are not necessarily those of my employers. |#=-

>It's not reserved for the filesystem, but rather for root.  Read about
>the -m option in the manpage to adjust that 5%.
>Investigate the -m option of mkfs.ext2/3 or tune2fs.
>The default is 5%.
Thanks for the info.

I found a post previously that claims it is required to prevent high 
levels of fragmentation as well as "other, very important" reasons. I 
wonder how accurate this statement is.
>Ummm, the 5% reservation is to prevent the high levels of
>fragmentation that occur when the filesystem is near full (something
>that I wish Windows would adopt as standard too ;-).  It is also to
>keep your system from "hanging" if system/root processes need to
>write to the filesystem, so they aren't at the "mercy" of
users
>filling it up.  And there are a few other, very important reasons
>too.
-- 

Maurice Volaski, mvolaski at aecom.yu.edu
Computing Support, Rose F. Kennedy Center
Albert Einstein College of Medicine of Yeshiva University