Thirty sandboxes in a cupboard
A data team keeps 30 old test servers, one for each project. Each one uses a little of its power. Together they fill a cupboard, hum all day and cost a lot to cool.
A consultant says: "Put them all in three big servers, as pretend computers made of software." Is it a good plan? What could go wrong?
Key words
| Word | What it means |
|---|---|
| Virtual machine | a computer made of software that runs inside a real one |
| Host | the real computer that runs the virtual machines |
| Hypervisor | software that makes and runs virtual machines |
| Overhead | extra work a system does just to run itself |
| Carbon footprint | the greenhouse gas made by what you use |
| Disaster recovery | getting systems working again after a big failure |
| Resilience | the ability to keep working or recover after a fault |
| Virtualisation | making a software copy of something real |
| CPU | the main processor of a computer |
| Snapshot | a saved copy of a virtual machine at one moment |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can give the benefits and the drawbacks of using virtual environments.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Fewer machines cost less
With virtualisation, many servers become VMs on a few hosts. You buy fewer machines, use less space and pay less for power and cooling. This is cost effective for a large environment. It matters most when you have many servers.
It also lowers the carbon footprint, because fewer machines mean less electricity and less to make.
Worked example: 30 servers become 3 hosts
| Plan | Machines | Each one can hold | Machines to power and cool |
|---|---|---|---|
| Before: one server for each project | 30 | 1 project | 30 |
| After: virtual machines on hosts | 3 | 10 VMs | 3 |
| Saving | 27 fewer machines |
The cells students fill in are left blank in this preview.
Management, resilience and recovery
A VM is easy to manage. You make one in minutes, copy it, move it and save a snapshot, all from one screen.
Resilience improves: if a host fails, its VMs can start on another. Disaster recovery improves too, because a VM is just files. You can keep a copy off site and start it anywhere after a fire or a flood.
Testing and learning in safety
A VM is a safe place to test. You can try a new update, break it, and roll back with a snapshot. You can test many system versions on one computer.
It is also good for education and training. Each student gets their own VM, can make mistakes freely, and starts fresh next lesson.