#CS#OS#Virtualization
Hypervisor: Type 1 vs Type 2
Conductor of VMs. Is the CEO running it directly (Type 1), or hiring a manager (Type 2)?
March 21, 2025
Codemapo
Conductor of VMs. Is the CEO running it directly (Type 1), or hiring a manager (Type 2)?
Why does my server crash? OS's desperate struggle to manage limited memory. War against Fragmentation.
Two ways to escape a maze. Spread out wide (BFS) or dig deep (DFS)? Who finds the shortest path?
Fast by name. Partitioning around a Pivot. Why is it the standard library choice despite O(N²) worst case?
Establishing TCP connection is expensive. Reuse it for multiple requests.
While containers (Docker) are lightweight and share the host OS kernel, Hypervisors provide strong isolation by giving each VM its own kernel. This makes Hypervisors better for multi-tenant environments where security and complete separation are paramount. However, containers win on startup speed and resource density. Modern tech like Firecracker (used by AWS Lambda) combines the best of both: the isolation of a MicroVM with the speed of a container.
Q: Can I run a Type 1 hypervisor on my laptop? A: Theoretically yes, but it's not practical. Type 1 hypervisors (like ESXi) expect to own the hardware completely. Running them on a laptop with drivers for Wi-Fi, Sound, and Graphics is difficult. Use Type 2 (VirtualBox, VMware Workstation) for laptops.
Q: Is Docker a Hypervisor? A: No. Docker uses the host kernel's features (Namespaces, Cgroups) to isolate processes. It does not virtually simulate hardware.
Understanding hypervisors clarified how the cloud works. When I launch an EC2 instance on AWS, the Nitro hypervisor creates my VM on a physical server. If I choose t3.medium, I get 2 vCPUs and 4GB vRAM. That server is probably running dozens of other VMs.
Locally, I use Type 2. I create an Ubuntu VM in VirtualBox to experiment with Kubernetes clusters. If it breaks, I restore a snapshot. After testing thoroughly, I deploy the actual service to the cloud's Type 1 environment (EC2).
Type 1 is for speed and efficiency. Type 2 is for convenience and experimentation. Both achieve the same goal—letting multiple OSes share hardware—but the installation location and performance trade-offs differ. Now, when someone asks, "What's a hypervisor?" I can say, "It depends on where it's installed."