3. Identify the attributes of these application deployment types
📘Cisco DevNet Associate (200-901 DEVASC)
A Virtual Machine (VM) is a software-based simulation of a physical computer. It acts like a real computer but runs on top of another computer (called the host) using a layer called a hypervisor. VMs allow multiple “computers” to run on a single physical machine.
Think of VMs as “computers inside a computer” – each VM can have its own operating system, applications, and network settings, independent of the host system.
1. Components of a Virtual Machine
Every VM has the following key parts:
- Virtual CPU (vCPU) – The CPU that the VM uses, allocated from the host’s physical CPU.
- Virtual Memory (vRAM) – Memory assigned to the VM from the host system.
- Virtual Storage (vDisk) – A file on the host that acts as a hard drive for the VM.
- Virtual Network Interface Card (vNIC) – Allows the VM to connect to networks, just like a real computer.
These components make the VM operate independently, almost like a real computer.
2. Role of the Hypervisor
A hypervisor is software that creates and manages VMs. There are two types:
- Type 1 (Bare-metal) – Runs directly on physical hardware. Example: VMware ESXi, Microsoft Hyper-V.
- Type 2 (Hosted) – Runs on top of a regular operating system. Example: VirtualBox, VMware Workstation.
The hypervisor ensures that each VM is isolated and gets the resources it needs, while sharing the underlying physical hardware efficiently.
3. Key Attributes of Virtual Machines
Here are the main characteristics you need to know for the exam:
- Isolation – Each VM runs separately. Problems in one VM do not affect others.
- Encapsulation – A VM is usually a set of files (configuration + virtual disk), making it portable and easy to backup.
- Resource Allocation – CPU, memory, storage, and network can be assigned and adjusted per VM.
- Multiple OS Support – You can run different operating systems (Windows, Linux, etc.) on the same host simultaneously.
- Snapshot/Cloning – You can take a “snapshot” of a VM at a point in time and restore it later. You can also clone a VM to create an identical copy quickly.
- Hardware Independence – VMs do not rely on the host hardware directly; they use virtualized hardware, so they are portable across different physical systems.
4. Advantages in IT Environments
- Server Consolidation – Many VMs can run on one physical server, reducing hardware costs.
- Testing and Development – Developers can run multiple environments on a single machine without conflict.
- Disaster Recovery – VMs can be backed up and restored quickly, reducing downtime.
- Isolation of Services – If one VM crashes or gets compromised, it does not affect others.
5. Limitations to Know
- Performance Overhead – Because VMs use virtualized hardware, they are slightly slower than physical machines.
- Resource Contention – Too many VMs on one host can compete for CPU, memory, and storage, affecting performance.
- Complex Management – Running many VMs requires monitoring and careful resource planning.
6. Common IT Examples (Without Non-IT Analogies)
- Running a Linux VM on a Windows server to host a web application.
- Creating a VM to test a new software update without affecting production systems.
- Using snapshots of a VM to quickly restore a database server to a previous state.
✅ Exam Tip
When the exam asks about VMs, remember:
- VMs simulate physical computers.
- They are isolated and portable.
- They require a hypervisor.
- They are flexible (different OS, snapshots, cloning).
- They are widely used for testing, development, and server consolidation.
