== sanity test 56Db: test 'lfs df -m' only shows MDT devices ========================================================== 00:06:05 (1787803565)
UUID                   1K-blocks        Used   Available Use%  Mounted on
lustre-MDT0000_UUID      1414116       11264     1260040   1%  /mnt/lustre[MDT:0] 
lustre-MDT0001_UUID      1414116       15956     1255348   2%  /mnt/lustre[MDT:1] 
lustre-OST0000_UUID      3833116       29000     3577908   1%  /mnt/lustre[OST:0] 
lustre-OST0001_UUID      3833116       14588     3592012   1%  /mnt/lustre[OST:1] 

filesystem_summary:      7666232       43588     7169920   1%  /mnt/lustre