Prove the provider cannot see inside the guest

applied · 60 min · Objective 3.3

Task

Demonstrate the gap between platform metrics and in-guest metrics by consuming memory and disk inside a VM and observing what each view reports. This is the measurement gap that causes real right-sizing mistakes.

Steps

  1. Start the guest with a fixed memory allocation. Record what the HYPERVISOR reports for its memory, and what free -m reports INSIDE it, in lab/agent.csv.
  2. Inside the guest, allocate and touch a large block of memory so the guest's used figure climbs substantially. Record both views again.
  3. Fill a filesystem inside the guest to over 90%. Record what the hypervisor reports for the virtual disk and what df -h reports inside.
  4. Install a monitoring agent in the guest that exports memory and disk usage, and confirm the exported figures match the in-guest view.
  5. Write in lab/agent.md the two metrics that require an agent, and the sizing mistake that follows from omitting them.

Verify

awk -F, 'NR>1 && NF>=3 {n++} END {print n" paired observation(s)"}' lab/agent.csv
grep -Eci 'memory' lab/agent.md
grep -Eci 'disk|filesystem' lab/agent.md
grep -Eci 'agent' lab/agent.md

At least three paired observations where the two views DIFFER. If they always agree, the guest's memory was never actually touched -- allocation alone is not enough, the pages must be written.

This is an independent study companion for CompTIA Cloud+ CV0-004 and is not produced by or endorsed by CompTIA.