"ext2: No robustness guarantees on system crash at all.
ext3: In the default data=ordered mode it is safe, because data is written before metadata. If you crash before the data is written (5 seconds by default) you get the old data. With data=writeback mode it is unsafe.
ext4: Currently unsafe, with a quite long window where you risk data loss. With the patches queued for 2.6.30 it is safe.
btrfs: Currently unsafe, the maintainer claims that patches are queued for 2.6.30 to make it safe
XFS: Currently unsafe (as far as i can tell), however the truncate and overwrite method is safe."
