Installation Guide, Windows Server 2008 R2 on HP Integrity Servers v7.1 (T2369-90032, March 2011)

On mid-range servers, the default behavior is for shutdown /s to cause
nPartition hardware to be powered off. Use the EFI Shell command
acpiconfig disable softpowerdown instead to make cells remain at a
wait at BIB state.
102 nPartitioning