What does 'Can't sync file './database_name/…frm' to disk (Errcode: 28)' mean?

I am getting this error message whenever I try to create a new index or a new table in my mysql server. Does anyone know what the reason is? This is the ouput after I run df -a

Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              13G  7.3G  4.5G  63% /
/dev/sda1             251M   27M  212M  12% /boot
tmpfs                 3.9G     0  3.9G   0% /dev/shm
10.156.248.29:/vol/pharos_pnxd_data_01/env_empty_sbid_27133_qdcprod
                       30G   30G   32K 100% /app

Solution 1:

It probably means that the device is out of space:

# perror 28
OS error code  28:  No space left on device