Backup and Replication: What is the Difference?
How do backup and replication compare?
Can one be used in place of the other? We’ve created a comparison table to explain some of the distinctions:
Backup vs. Replication
Backup involves making a copy or copies of data.
Replication is the act of copying and then moving data between a company’s sites. It is typically measured in Recovery Time Objective (RTO) and Recovery Point Objective (RPO).
Backup requires a tape library (usually VTL doing disk-to-disk backup) and some place to store archived tapes.
Replication requires investment in another, identical, infrastructure, effectively doubling your IT costs.
Backup focuses on compliance and granular recovery, such as recovering a single user’s emails from 5 years ago.
Replication and recovery focus on business continuity — quick and easy resumption of operations after a disaster or corruption. Minimizing the recovery time objective (RTO) is key.
Backup is typically used for everything in the enterprise, from critical production servers to desktops.
Replication is often used for mission-critical applications that must always be up and running.
How it Works
Backup typically relies on snapshots which are copies of the data set taken at a pre-determined point in time.
Replication can be synchronous, asynchronous or near-synchronous and may use Continuous Data Protection (CDP) to enable users to access historic images.
Relatively inexpensive way to avoid data loss. Valuable for compliance. Does not ensure continuity of operations.
Focused on ensuring that business applications and processes are always available, even after a disaster. More expensive to set up and maintain.
This table begs the question asked by Chris Mellor in a post on The Register (which is a great resource on the subject):
“Can replication replace backup?”
“Backup started as saving a copy of data to tape. For many users it now means saving a copy to disk, either as a straight file backup or as a virtual tape backup. In both instances data is being moved from one disk to another. That’s what replication does too… Does this mean you can dump your backup software and rely completely on the much simpler replication idea?”
The experts quoted in Chris’ post respond with varying shades of “no”. Replication still has a higher cost than backup, and some companies are legally required to retain their physical tapes for a certain number of years. At Zerto, sometimes we hear the question asked the other way,
“Can backup files shipped to a remote location replace replication?”
We don’t think so.
For one, backup snapshots taken at regular intervals throughout the day will significantly slow down your production environment. For more info on this, read Marcel van den Berg’s post, “Know the Performance impact of Snapshots!” Even if you take fewer backup snapshots in order to protect your production environment, you’ll be at risk of losing large chunks of data if you have an outage or disaster.
Second, backup solutions simply don’t scale well when used for replication. They work best in smaller environments with less critical data.
Third, and most important, having access to your data at a remote site is only the first step of a reliable disaster recovery (DR) plan. For a DR plan to be successful, business processes need to be fully operational after a disaster or outage; having data on a disk does not achieve that goal. Particularly in virtualized infrastructures which are expansive, always changing and often large scale, shipping backups is not a viable solution for a quick recovery following a disaster. Only continuous replication provides a true business continuity solution for the enterprise. Backup, even shipped to a remote location, does not replace the always-available benefits of replication.
Bottom line: Backup and Replication have distinct use-cases and both have a place in an enterprise data center, the key is to determine your company’s objectives in order to find either backup or replication solutions that match your needs. However, if your company is looking for disaster recovery and always-on data protection, replication is likely a better option.
You can find more details on Disaster Recovery Planning with Zerto Virtual Replication here.