The problem can happen when you are trying to install/reinstall MacOS and FileVault is active but optimizing is not yet completed.
Go the Recovery mode (hold cmd + R during boot)
— open a terminal, and type:
diskuitl cs list
In the Logical Volume you will find
Conversion Progress : Paused
— I opened a second terminal window
— Searched for the binary 'corestoraged':
find / -name 'corestorage*'
— found it in the recovery folder:
— Started corestoraged in the found folder:
— Check the HD via the first terminal, the Conversion progress now showed a percentage, after a hour the hd was converted.
— than I could reinstall El capitan from the same recovery mode.
— After the reinstall everything was like it was.