Multilayered film stacks, with length scales less than 10 nm are commonly used ina variety of devices, but present significant challenges to mechanical testingand evaluation. This is due to property convolution of the different layers.Both the properties of the individual layers and the combined response of thefilm stack are important input for design optimization. Here, we presentex-situ nanoindentation of a film stack representative of aperpendicular magnetic recording (PMR) hard disc drive (HDD), with more than 10layers. We then compare this with in-situ transmission electronmicroscopy indentation to visualize deformation of individual layers of thestack. The ex-situ testing reveals early plastic deformation,with an initially high contact pressure (13 GPa) and modulus ( >160GPa), followed by significant softening (8 GPa contact pressure and 140 GPamodulus), then slight hardening to 9 GPa. From in-situ testing,it is revealed that the metallic layer directly under the diamond like carbon(DLC) contributes the majority of the deformation and plastic flow, which is inturn constrained by a metallic oxide.