I was happy to complete my first WU yesterday (600 hours of computation), the results upload was successful but disk space on my computer was not freed as expected. the WU was done with 4.10 release. the new WU is in 4.12, maybe it would be better. For work-around, I try to delete the directory of the old WU to free disk space (more than 300 Mb leaving on about 700 Mb use at the end of the project). It seems to be OK.

Is it a referenced bug ? And is it fixed in current or planned in future release ?

It's not a bug. Only a small part of the model is uploaded; the rest remains on your computer.
Read <a href="http://www.climateprediction.net/board/viewtopic.php?t=2951"> this</a> post for more information.