OS extension, also known as kernel-based virtualization, refers to a type of virtualization where a VMM (Virtual Machine Monitor) is implemented as an extension of the Host OS kernel. While OS extension has many advantages, such as efficient resource management and low overhead, it also has some disadvantages, including:
Complexity: OS extension involves modifying the Host OS kernel, which can be a complex and error-prone process. The VMM code must be carefully integrated with the kernel code to ensure stability and reliability.
Security: OS extension introduces new attack vectors that can be exploited by attackers. Since the VMM code runs in kernel mode, any vulnerabilities in the VMM can be used to compromise the entire Host OS.
Compatibility: OS extension may not be compatible with all hardware and software configurations. Since the VMM code is tightly coupled with the Host OS kernel, it may not be able to support certain hardware devices or software applications.
Performance: While OS extension has low overhead compared to other virtualization technologies, it may still introduce some performance degradation due to the extra layer of abstraction and the need for context switching between the Host OS and the Guest OS.
Scalability: OS extension may not be scalable to support large numbers of virtual machines or workloads. The VMM code may become a bottleneck as the number of virtual machines increases, and the Host OS may need to be restarted frequently to maintain stability.
In summary, OS extension has some disadvantages, such as complexity, security, compatibility, performance, and scalability, that need to be carefully considered when choosing a virtualization technology.
