Dear all After I newly created a ext4 fs and check the mb_group, #group: free frags first [ 2^0 2^1 2^2 2^3 2^4 2^5 2^6 2^7 2^8 2^9 2^10 2^11 2^12 2^13 ] #0 : 23513 1 9255 [ 1 0 0 1 1 0 1 1 1 1 0 1 1 2 ] #1 : 31743 1 1025 [ 1 1 1 1 1 1 1 1 1 1 0 1 1 3 ] ^^^^ #2 : 32768 1 0 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ] #3 : 31743 1 1025 [ 1 1 1 1 1 1 1 1 1 1 0 1 1 3 ] #4 : 32768 1 0 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ] #5 : 31743 1 1025 [ 1 1 1 1 1 1 1 1 1 1 0 1 1 3 ] #6 : 32768 1 0 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ] #7 : 31743 1 1025 [ 1 1 1 1 1 1 1 1 1 1 0 1 1 3 ] #8 : 32768 1 0 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ] #9 : 31743 1 1025 [ 1 1 1 1 1 1 1 1 1 1 0 1 1 3 ] #10 : 32768 1 0 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ] #11 : 32768 1 0 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ] There are some bgs that have 1024 blocks allocated. What are they for ? Many thanks in advance Jianchao