Greetings!
If the chassis already has a 12 LFF drive Cage then it should come with a built-in expander. All drives can be driven off of the embedded P420i controller.
Few points to be noted:
The 8LFF, 12LFF, and 25SFF drive cage versions are not field upgradeable options from the 8SFF model.
Compatible storage controllers for DL380p Gen8 servers support up to 6Gb/sec transfer rate.
All 12G SAS Hard drives only operate at 6G speeds in the DL380p Gen8
https://h20195.www2.hpe.com/v2/getdocument.aspx?docname=c04123238
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