We often hear the words backup and replication, whether alone or together, these terms play a central role in disaster recovery and business continuity strategies. However, what is the difference between the two? And why do most DR providers encourage their clients to have both?
A backup is a process of making a copy of data and storing it offsite. Backup can be done to tape, which requires a tape library and physical storage space, becoming more common is backing up to disk either in the ‘Cloud’ or on a second site.
Accessing a backup solution is not expensive for businesses and can be used for making a copy of almost everything within the organisation, from servers to desktops.
A backup solution is perfect for compliance and archiving purposes as it provides copies of data at a specific point in time. However, backup alone does not ensure business continuity or disaster recovery after an outage or in the case of disruption.
Replication is a process of copying data and moving it within a company’s sites (e.g. data centre, colocation facility, public or private cloud).
Contrary to a backup solution, replication can be expensive as it may require the organisation to invest in additional physical infrastructure, where critical applications that must always be up and running are replicated to.
The purpose of replication is to ensure business continuity and availability even after an outage or disruption. This is the biggest element that differentiates replication from backup.
Why do you need both?
Although backup and replication have two different functions and purposes, they tend to complement each other. Indeed, when used together, they provide a comprehensive business continuity plan.
With replication, because the data is synchronised to the off-site location, the data itself is constantly changing. For example, in the case of a natural disaster, a business can relocate its staff to the replicated location, enabling it to reduce its Recovery Time Objective (RTO) and carry on business as usual.
However, because the data in the replication site is constantly changing, it makes it hard for an organisation to establish a point in time from which initiate the recovery. For example, if an employee accidentally deletes an important file from the production server, with replication it will also be deleted from the replica server. Where do you then recover the files from?
These are the kind of situations where backup makes the difference. If a business carries out regular backups, then it will be able to restore the file from the last backup effectively prevent data loss in the event of accidental deletion. This is because a complete backup gives the business a point in time from which to recover the data. This is why backups are very good at reducing the Recovery Point Objective (RPO).