Opennebula shows wrong datastore capacity

I have installed OpenNebula following the quickstart guide OpenNebula on CentOS 6 and KVM.

I am using all local hard disks. I have one huge software RAID10 array composed of 4 partitions, no LVM whatsoever. The raid device is /dev/md2 and is mounted on /var/lib/one/datastores.

Here is the disk space as reported by CentOS:

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/md2        7.1T  177M  6.8T   1% /var/lib/one/datastores

and here is the disk usage as reported by CentOS:

$ du -shc /var/lib/one/datastores
20K     /var/lib/one/datastores
20K     total

so, the folder seems pretty much empty (although I still don't know why df -h says that 177M are used, but anyway).

and here is the contents of the folder:

$ ls -la /var/lib/one/datastores
total 24
drwxr-xr-x 6 oneadmin oneadmin 4096 Jul 31 18:19 .
drwx------ 8 oneadmin oneadmin 4096 Jul 31 18:33 ..
drwxrwxr-x 2 oneadmin oneadmin 4096 Jul 31 18:20 0
drwxr-xr-x 2 oneadmin oneadmin 4096 Jul 31 18:20 1
drwxr-xr-x 2 oneadmin oneadmin 4096 Jul 31 18:04 2
drwxr-xr-x 2 oneadmin oneadmin 4096 Jul 31 18:13 .isofiles

$ find /var/lib/one/datastores
/var/lib/one/datastores
/var/lib/one/datastores/2
/var/lib/one/datastores/.isofiles
/var/lib/one/datastores/1
/var/lib/one/datastores/0

The problem is that OpenNebula says my datastores are using 367.8GB when they should be empty. See the screen shot.

Update: I have tried stopping OpenNebula, deleting the database /var/lib/one/one.db and starting OpenNebula again with no positive result.