Backup and DR can be separate systems, but do not have to be. Modern advances in backup and DR technology make it possible to have a single integrated system to satisfy the needs of both, and I can think of no reason to not use such a system.
Serving backup and DR needs with a single system is nothing new, as we were doing this over 20 years ago. When I joined the IT industry in 1993, backup and DR used the same storage target: tape. You backed up your data center to tape every day, you put those tapes in a case, and your off-site vaulting company picked them up and took them away. Best practices were to have a tape copy on-site and off-site; on-site tapes were used for day-to-day operational restores, and off-site tapes were hopefully never used. They were for disaster recovery, and you hoped that day would never come.
This was before the ubiquity of RAID, so the loss of a single disk drive could mean the loss of the operating system, the application, and even all of the data. This is why we became good at what is now called bare-metal restore. We were regularly testing our ability to restore one or more servers just because of small-scale disasters that would happen inside the data center. Then in a real disaster we simply used the same system for DR that we had been using for operational recovery.
Then backups and DR diverged when that same company switched to replication for DR and started using RAID to protect all valuable data. Backups became used only to restore from operator error and malware attacks or the occasional double drive failure. Even if we did test our backups, they had nothing in common with the replicated copies of the data stored off-site. The point is there was nothing magical about having DR and backup needs served by multiple applications; it’s just something that happened as technology changed.
Today it is possible, once again, to have a single system that stores a copy of data on-site and off-site and can serve as both a backup and a disaster recovery system – and I think this is a good thing. It’s less expensive to have a single system serve multiple purposes. More importantly, It means that no matter where your test your recoveries, you’re testing both the backup and DR systems. Such systems also support automated testing of backups, something which wasn’t really possible back in the day.
Therefore, I think that it is perfectly fine to serve backup and recovery needs from a single system. In fact, it may actually have a higher level of data protection than doing the opposite.