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Well the question says most of it...

Gparted reports the used space as 4.86 GB
Nautilus reports used space as 15.1 GB...(via Properties of /media/U_0298_data)

Why is this space used? and who is reporting the correct figure? (...if either)
Is this related to the Trash?

PS. It is the only partition, and is using the entire drive space.

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3 Answers 3

up vote 19 down vote accepted

Gparted, that use mkfs.ext4 to create a ext4 filesystem, reserves 5% of the space for super-user, as explained in man page:

-m reserved-blocks-percentage
   Specify  the  percentage  of the filesystem blocks reserved for the super-user.  This 
   avoids fragmentation, and allows root-owned daemons, such as syslogd(8), to continue to 
   function correctly after non-privileged processes are prevented from writing to the 
   filesystem.  The default percentage is 5%.

Now, 5% of about 300GB is just the 15GB you see already used.

More interesting, you can avoid this if you feel do not need it, simply creating the filesystem with, for example,

sudo mkfs.ext4 -m 0 /dev/sda1

where 0 means 0%.

I think Gparted see more space because is run by super-user, so part of that 15GB are free for him. Nautilus is run by the user, so the space is less.

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1  
Grazie mille... –  Peter.O Oct 8 '10 at 7:54
7  
You can also reset the reserved percentage after you create the filesystem with tune2fs. The syntax is essentially the same: sudo tune2fs -m 0 /dev/sda1. –  Matthew Crumley Oct 8 '10 at 15:10

There are different ways of counting space on a filesystem ranging from bytes not in use to free clusters, etc. In the absence of better information, I'd take gparted's report as more "accurate".

Filesystems require overhead for i-tables, free lists, superblocks, superblock backups, and - in ext4 - journaling. Your reported 4.86 out of 298GB is a whopping 1.6% overhead in order to keep track of your stuffs; that strikes me as pretty low overhead.

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low overhead? Ouch! –  MestreLion Jun 13 '11 at 19:33
    
I have a pretty similar question here: askubuntu.com/questions/48488 Its a 250GiB parition, so figures are similar. Nautilus show 188MB of used space, and a total capacity thats 4GB smaller than actual. Which one is the overhead? And what is the other? –  MestreLion Jun 13 '11 at 19:37

Aside from the space reserved for root, see my other answer here. The short of it is that the ext series of filesystems reserves space for the inode tables at format time, which with the default settings, amounts to 2 mb for every 128 mb of disk space.

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