[Ocfs2-users] df & du - that old chestnut
Nigel Bishop
Nigel.Bishop at ioko.com
Thu May 7 04:14:42 PDT 2009
Afternoon,
We have an ocfs2 release 1.4 filesystem shared between two nodes
(RHEL5). The filesystem in question is used exclusively for Oracle RMAN
backups.
A df -h shows the following:
[root at imsthdb07 ~]# df -h /data/orabackup
Filesystem Size Used Avail
Use% Mounted on
/dev/mapper/eva_mpio_myserver07_08_oracle_bkup0 250G 198G
53G 79% /data/orabackup
While a du -sh shows that 62G is used
I read Sunil Mushran's article on the reported differences between df &
du and that sort of makes sense (maybe I'm missing something). The
filesystem was created with a Blocksize and Clustersize of 4Kb and is
mounted with the following parameters:
/dev/mapper/eva_mpio_myserver07_08_oracle_bkup0 /data/orabackup
ocfs2 _netdev,nointr,defaults 0 0
We have a RMAN retention policy of 3 days so backups older than that do
get deleted.
As a test I did a df & du of this filesystem and then deleted (via RMAN)
the oldest backup, this file was 17Gb in size, after which I again did a
du & df. These both reported that 17Gb had been released to the
filesystem.
What I still don't get is why df reports that the Used space is at 198Gb
- that seems an awful waste
Any insight into this major discrepancy would be much appreciated.
Thanks,
Nigel
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