RPO vs RTO Explained
What RPO and RTO Measure
RPO vs RTO compares two targets used to plan recovery. The recovery point objective (RPO) is the most data, measured in time, that you can afford to lose. The recovery time objective (RTO) is the longest time your site can be down before the outage becomes unacceptable.
For example, an RPO of 24 hours means the last usable copy can be no more than a day old. An RTO of four hours means the site must be running again within four hours of a failure. RPO is about lost data, while RTO is about downtime. A site can meet one target and miss the other.
A complete plan that uses these targets is covered in disaster recovery plans for websites.
How RPO and RTO Shape Backup Choices
- RPO sets backup frequency. A 24-hour RPO can be met with daily copies. A one-hour RPO needs copies at least hourly, or a method that captures changes continuously. The frequency question is explored in how often to back up a website.
- RTO sets the restore method. A short RTO favours backups that can be restored quickly, such as a full server image or a standby copy. A restore from slow or distant storage may take far longer than the target allows.
- Both targets have costs. Tighter targets need more storage, more bandwidth and more administration. Looser targets are cheaper to meet but accept more risk.
Good targets come from the business impact of an outage. A site that takes orders may need a short RPO and RTO, while a brochure site may accept longer gaps.
A Shop and a Brochure Site Compared
A busy online shop sets an RPO of one hour, so that no more than an hour of orders can be lost. It sets an RTO of two hours, because each hour offline means lost sales. To meet these targets, it runs frequent database copies and keeps a full server image ready for fast restores.
A company brochure site sets an RPO of one week and an RTO of two days. Its content changes rarely, and a few days offline costs little. Its simpler weekly backups meet those targets without extra effort.
Frequently asked questions
Can RPO Be Zero?
A zero RPO means no data loss at all. It requires techniques that copy every change as it happens, such as continuous replication. These are costly and complex, so they are usually reserved for systems where any lost transaction is unacceptable. Most websites set a practical RPO that is greater than zero.
Which Matters More, RPO or RTO?
Neither is more important in general, because they answer different questions. RPO asks how much data you can lose, and RTO asks how long you can be offline. A site that loses little data but stays down for days may still fail its business needs, so set both.