I think mostly because of dedication of the maintainer (Szabolcs
Szakacsits). I don't claim fuse has a great part in it, except the
obvious advantages of developing in userspace: no kernel crashes,
easier debugging, etc...
And of course it could be ported back to the kernel (ntfs-3g is GPL
too), and that would probably result in even more speedups. But
that's not a trivial task either.
Miklos
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