Who is right about inodes? df or tune2fs?

Question

On my Redhat 6.5, I get two different results on free inodes.

Using df :

[root@xxxx ~]# df -i /dev/mapper/data_vg-data_lv 
Filesystem                   Inodes IUsed   IFree IUse% Mounted on 
/dev/mapper/data_vg-data_lv 2555904 72422 2483482    3% /data/cfa000/x1/data 

Using tune2fs :

[root@xxxx ~]# tune2fs -l /dev/mapper/data_vg-data_lv | grep -i inode 
...
Inode count:              2555904 
Free inodes:              846816 
...

Can this situation be normal? If not, what could be the problem?

Solution

df should be correct. tune2fs inode count is not checking the superblock kept in memory so it's unreliable for mounted volumes. If you unmount /dev/mapper/data_vg-data_lv and check with tune2fs it should show the same values as df -i

Comments

[Pozinux]

I'm connected through ssh on this server so I'm sure. What do you mean by latest erratas please?

[Pozinux]

Ok I'm going to unmount it and test later on. However, I have another server which is the same as this one with same FS mounted and both df -i and tune2fs -l show the same value. Also, the difference inode count seems so big.

[HoD]

Are you using different filesystems on the two servers? As I understand it the ext4 superblock is only written to disk when unmounting, but it's possible different filesystems update sooner.