Memory hook: Virtual hardware still consumes real resources.
Must remember
A hypervisor presents virtual hardware to guest operating systems. Type 1 runs directly on the host platform; Type 2 operates through a host OS. VMs isolate guest kernels; containers usually share a host kernel. Neither removes the need to patch, authorize access or back up data.
Plan CPU virtualization support, memory, storage and network capacity for concurrent guests. Overcommitting memory or disk can harm both host and guests. Virtual switches/network modes determine reachability: NAT, bridged/external and host-only/internal modes solve different needs. Do not expose a practice VM to a production network unintentionally.
Snapshots/checkpoints capture a recoverable state under the platform's model; they can grow and are not a substitute for independent backups. Clones create separate instances whose identities, licenses and credentials need review. VDI delivers centrally hosted desktops; local virtualization runs guests on the endpoint.
Cloud IaaS provides infrastructure, PaaS a managed application platform and SaaS a managed application. Public/private/hybrid/community describe deployment arrangements. Elasticity responds to changing demand; scalability is the ability to grow; high availability reduces outage impact.
Shared responsibility changes operational duties, but customer data, identities and configurations still need protection. Pay-as-you-go shifts cost patterns without guaranteeing savings. Network dependence, data location, subscription licensing and backup/recovery remain part of support.
Common endpoint uses include testing, legacy applications, isolated development and training. Select a supported, licensed environment and verify both guest functionality and host health.
Choose under exam pressure
| Requirement | Choice and reason |
|---|---|
| Test another OS without replacing the main OS | A suitably resourced virtual machine. |
| Centrally delivered corporate desktops | VDI or an appropriate desktop-as-a-service solution. |
| Use a completed web application | SaaS rather than managing its underlying VM stack. |
Traps
- A snapshot stored with the VM can be lost with the same storage failure.
- Virtualization isolation is not permission to run untrusted code without controls.
Active recall
1. Type 1 versus Type 2?
Type 1 runs directly on the host platform; Type 2 depends on a host OS.
2. Do containers normally have separate kernels?
No, they generally share the host kernel.
3. Elasticity versus scalability?
Elasticity adjusts resources with demand; scalability is the capacity to grow.
4. Why monitor snapshot growth?
It can consume storage and degrade or halt workloads.
5. Who protects tenant data in SaaS?
The provider and customer have defined duties; the customer retains important data/access responsibilities.