IS> Wait - is the file *name* 50MB big?
New compression scheme -- files can now be completely empty
and yet contain everything.
Jokes aside, I think.when.JFS+ gets compression support in osx 10.6 (snow leopard) compressed files looked exactly like 0-sized by usual ls or file if looked from previous version of IS (just Leopard, 10.5.x).
At least this is what I see on powerpc mac running 10.5 and 10.6 alpha (community version pieced together).
About long disk activity on udf packetwriting - may be it tries background format?