Virtual Machine

    
Virtual Machine

1. Virtual Machine (VM) 

Definition:

A Virtual Machine (VM) is a software-based emulation of a physical computer that runs an operating system and applications, just like a real computer.

Key points:

• Created and managed by a hypervisor.

• Runs on virtual hardware (virtual CPU, memory, disk, network).

• Provides isolation between different VMs.

• Example: Running Windows inside VMware on a Linux laptop.

2. Life Cycle of a VM

Think of it like the life stages of a living thing, but for a virtual computer.

1. Creation

     • VM is defined with CPU, memory, storage, and network settings.

• Operating system is installed or imported.

2. Power On / Start

• VM is booted and the guest OS starts running.

3. Running

• VM executes applications and performs tasks.

4. Suspend / Pause

• VM state is saved in memory or disk, execution is halted temporarily.

5. Resume

• VM continues execution from the suspended state.

6. Shutdown / Power Off

• Guest OS is stopped, and VM resources are released.

7. Deletion

• VM configuration and virtual disks are removed.

📍 Exam diagram idea:
[Create] → [Start] → [Running] → [Suspend] ↔ [Resume] → [Shutdown] → [Delete]
3. VM Migration — Concept and Techniques
• Concept:
Moving a running or stopped VM from one physical host to another without affecting its execution significantly.
• Why needed?
• Load balancing between servers.
• Hardware maintenance.
• Energy saving.
Techniques:
1. Cold Migration
• VM is powered off, then moved to another host.
• Simple but causes downtime.
2. Live Migration
• VM is moved while still running, with minimal downtime.
• Memory and CPU state are transferred while VM is still active.
3. Storage Migration
• Moving the VM’s virtual disk files to another storage location.

4. VM Consolidation 
Concept:
Combining workloads from multiple VMs onto fewer physical servers to save resources.
• Purpose:
• Reduce power consumption.
• Lower hardware costs.
• Improve resource utilization.
• How it works:
• Identify underutilized VMs.
• Migrate them to fewer hosts.
• Power off unused servers.
📍 Example:
If 5 servers are each running at 20% capacity, consolidate into 2 servers running at ~50%, and turn off 3 servers.

5. VM Management — Concepts
• Concept:
The process of monitoring, controlling, and maintaining VMs for performance, security, and availability.
• Tasks in VM Management:
1. Provisioning — Creating new VMs and allocating resources.
2. Monitoring — Tracking CPU, memory, network usage.
3. Backup & Recovery — Protecting VM data.
4. Security — Applying patches, controlling access.
5. Automation — Using scripts/tools to auto-scale or auto-heal.
✅ Exam Tips:
• Always include definition + purpose + example in answers.
• Diagrams for VM life cycle and migration types can fetch extra marks.
• Keep answers in point form for clarity in MSBTE papers.