/usr/libexec/storagekitd storagekitd is used by the StorageKit framework for disk state keeping and privileged operations.
/System/Library/PrivateFrameworks/StorageKit.framework/Versions/A/Resources/storagekitd storagekitd is used by the StorageKit framework for disk state keeping and privileged operations. It is used by various clients in macOS.
The binary is a part of StorageKit private framework.