UNIX for Dummies Questions & Answers

Hi all,

My system is running on RHEL4. I've just deleted 2 huge tablespaces from Oracle.
Then I saw the disk usage. The report by df differs from the du.

Do you know why they shows different results? Which one is correct?

Code:

[root@localhost ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
...
/dev/sdf1             1.1T  934G  111G  90% /disk6
...

[root@localhost ~]# du /disk6/ -hs
803G    /disk6/

Thank you very much

I would assume that they are both correct. You need to read the description of each command carefully.

"The df utility displays the amount of disk space occupied by currently mounted file systems, the amount of used and available space, and how much of the file system's total capacity has been used."

"The du utility writes to standard output the size of the file space allocated to, and the size of the file space allocated to each subdirectory of, the file hierarchy rooted in each of the specified files."

The difference is space allocated to files which are not a part of the file hierarchy. One way a file can get in this state is for someone to rm it while it is open to a program. Now the file has no name (and thus is invisible to du) but it won't be deleted until the program closes it. Programs also intentionally do this to allocate a private temporary file that is guaranteed to disappear when they exit.