The shop that went quiet
An online shop has one server. On the busiest day of the year, a fan inside it stops. The server overheats and switches off.
For two hours, nobody can buy anything. The owner loses a lot of money.
A designer asks one question: how do we build this so one broken part does not stop everything?
Key words
| Word | What it means |
|---|---|
| Network | computers and devices joined together so they can share data |
| Resilience | the ability of a system to keep working when something goes wrong |
| High availability | a design with a main system and a spare, so work carries on if one fails |
| Primary | the system that does the work now |
| Secondary | the spare system that takes over if the primary fails |
| Failover | the switch from a failed system to its spare |
| Cluster | a group of servers that work together as one system |
| Scalability | being able to add more power when more people use the system |
| Load balancer | a device that shares incoming requests between servers |
| Segmentation | splitting a network, or its parts, into separate zones |
| Redundancy | having a spare part ready, in case the first one fails |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can explain four ways to build a resilient network: high availability, clustering, load balancing and segmentation.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
High availability: a main and a spare
High availability (HA) uses two systems. The primary does the work. The secondary waits.
The two keep checking each other. If the primary stops, the secondary takes over. This switch is called failover.
The users may notice nothing at all.
Clustering: a team of servers
A cluster is a group of servers that act as one system. They all do work at the same time.
A cluster gives two gains. If one server fails, the others carry on, so there is redundancy. If more people arrive, you add a server, so there is scalability.
HA is a main and a spare. A cluster is a team.
Quick check
Have a go
Quick check
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.