Android File Systems

YAFFS

Android in most mobile phones up to version 2.2 (Froyo) use the YAFFS2
filesystem.

Here is some information about YAFFS2:

According to this report by Ted Tso, version 2.3 (Gingerbread) will be
using ext4

With ext4, you may need to explicitly sync the data to the file system,
in order to make sure not to lose information.

See this blog entry by Tim
Bray
for information on this topic.