Hello everybody,
first of all thank you the development of Ext2/3/4. It works like a
charm and makes it possible to base applications on it.
However, now I have the first time where I need more information to
understand the behaviour of a ext4 installation on a 480 GB harddisk.
It holds a database with a size of 355 GB, as said by
"du -m":
...
355263 /opt/ssd
However, "df" says:
Filesystem 1K-blocks Used Available Use% Mounted on
...
/dev/sdc 468346644 409888536 35015532 93% /opt/ssd
I do understand why there is a gap between "Used" plus "Available" and
"1K-blocks", but I don't understand why "Used" is so much bigger (54 GB
difference) than what "du -m" indicates.
I can rule out any issues with inodes; "df -i" indicates that less than
one percent is used.
I tried to understand more details by using "debugfs". I thought I get a
full list of used blocks with:
for i in *; do { echo "blocks $i" | sudo debugfs /dev/sdc | grep -vE
"^debugfs" | awk '{ for (i=1; i < NF; ++i) print $i; }'; }; done
which delivered 90938943 lines (containing block numbers allocated by
visible files). But
echo "testb 1 117330000" | sudo debugfs /dev/sdc | grep "marked in use"
has delivered 102595007 lines (containing block numbers marked as "used").
I tried to learn more about blocks marked as "marked in use" but not by
a known file, and
echo "icheck 98304 98305" | sudo debugfs /dev/sdc
returned
debugfs: icheck 98304 98305
Block Inode number
98304 <block not found>
98305 <block not found>
Could somebody explain to be what the purpose of these 11,656,064 blocks
is that don't belong to an inode but are still marked as used?
Do I have a chance other than reformatting the drive to get back this space?
Best regards,
Roland
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