HI I have a problem with my fusion drive. After numerous attempts to reorder the partitions and install / remove a windows partition (why is that never easy?) my hard drive is well borked. I have effectively four partitions, but only one is visible. The new Disk Utility in El Capital tells me two are present, (one 1TB, and one 100GB) but wont let me access the 100GB one, even after running a first aid. So then, I have all my files backed up with TimeMachine, so no worries about zeroing the drive and reseting it completely. But how do I do this ? No such options are available in DiskUtility if I start up from the recovery mode ??