The shop that cannot stop
An online shop makes 500 pounds an hour. Its server fails at noon. The last backup was taken at 8 a.m.
Two questions matter. How long can the shop be down? And how many hours of orders can it afford to lose? Two measures answer them.
Key words
| Word | What it means | Example |
|---|---|---|
| Recovery time objective | The longest time a system may be down before the harm is too big. | RTO |
| Recovery point objective | The most data, measured in time, that the business can afford to lose. | RPO |
| Backup | A spare copy of data, kept so it can be restored. | |
| Downtime | The time a system is not working. | |
| Objective | A target you set before anything goes wrong. | |
| Restore | Copy data back from a backup. | |
| Server | A computer that gives data or services to other computers. |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can explain RTO and RPO and use them to decide how often to back up and how fast to restore.
Starter: what you already know
Have a go
Starter: what you already know
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Cycle 1: RTO is about time down
The recovery time objective (RTO) is a target. It says: the system must be back within this time.
If the RTO is 4 hours and the restore takes 6, the target is missed. The business loses more than it planned.
A short RTO needs spare servers, fast storage and a well-practised plan. It costs more.
Cycle 2: RPO is about data lost
The recovery point objective (RPO) is also a target. It says: we can lose at most this much data, measured in time.
If the RPO is 2 hours, backups must run at least every 2 hours. If the last backup is 5 hours old when the server fails, the target is missed.
A short RPO means frequent backups. It costs more.
Worked example: the online shop
| Measure | Target | What happened | Met? |
|---|---|---|---|
| RTO | 4 hours | Restored in 3 hours | Yes |
| RTO | 4 hours | Restored in 6 hours | No |
| RPO | 2 hours | Last backup was 1 hour old | Yes |
| RPO | 2 hours | Last backup was 4 hours old | No |
The cells students fill in are left blank in this preview.
Check: RTO or RPO
Have a go
Check: RTO or RPO
4 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.