[CentOS] HDD usage oddity

Stephen Harris lists at spuddy.org
Thu Nov 22 01:16:32 UTC 2007

On Wed, Nov 21, 2007 at 07:37:31PM -0500, Ugo Bellavance wrote:
> 	2 of my Centos4 servers are showing weird behavior.
> [root at server1 ~]# du -sh /var/
> 1.8G    /var/
> [root at server1 ~]# df -h /var
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/sda7             4.3G  3.9G  181M  96% /var

There are two things to consider.


If you have large block sizes and lots and lots of small files then
"du" will report a number quite a lot smaller than "df".  "df" reports
on actually amount free; "du" reports on apparent size of the files used.


If you delete a file that is still "open" (typically a log file, or
a file being written to in /var/tmp) then Unix doesn't actually delete
the file at that point; it removes the directory entry and marks the file
to be deleted when no one is using it any more.

I've seen developers create debug logs in /tmp that grew to 2Gb then
delete them to save space... while the program was still writing more
debug messages, so they didn't save any space at all.



More information about the CentOS mailing list