Hi @digitalbug,
I need to defragement by drives very often as I build new UE version which need to build compile Shaders
try this from the command line
REM you need to run tnis in Win Administrator shell
C:> defrag D: /H /M 16
This will run in the background
My system disk is an NVRAM SSD where I do all my build, so I need to use
the DEFRAG option Optimise to “Trim” my SSD