Historically, storage controllers have been extended by integrating new code, e.g., file serving, database processing, deduplication, etc., into an existing base. This integration leads to complexity, co-dependency and instability of both the original and new functions. Hypervisors are a known mechanism to isolate different functions. However, to enable extending a storage controller by providing new functions in a virtual machine (VM), the virtualization overhead must be negligible, which is not the case in a straightforward implementation. This paper demonstrates a set of mechanisms and techniques that achieve near zero runtime performance overhead for using virtualization in the context of a storage system.