> Question: > I'm just creating test-only f2fs images. If I create a very small image, > 100 MiB, overhead is 60%. Is that also correct? > Unfortunately, it's correct. In that case, f2fs occupies the volume as: # cat /sys/kernel/debug/f2fs/status [SB: 1] [CP: 2] [NAT: 2] [SIT: 2] [SSA: 1] [MAIN: 42(OverProv:25 Resv:25)], each of which shows [data_structure: # of segments]. In the case of 100 MB partition, f2fs provides 42 segments (84 MB) to main area which includes user data and index node blocks. The main reason of the space reduction is due to the over-provision space. By default, over-provision ratio is 5%, 25 segments (50 MB), for better cleaning performance. Note that, the over-provision ratio is tightly coupled with reserved space. If you try to decrease the ratio, f2fs reserves more sections to deal with worst-case cleaning scenarios. (e.g., 5% of over-provision ratio requires at least 20 reserved sections for cleaning successfully.) Thanks, -- Jaegeuk Kim Samsung
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