Azure Site Recovery enables physical on-premises, Azure Virtual Machines, Hyper-V and VMWare virtual machines to failover in case of a disaster and to failback once it has been resolved.
Initially, Microsoft’s disaster recovery solution was focused on storage, eventually expanding to disaster recovery-as-a-service; so now, it boasts near-constant data replication process, which makes it possible to keep copies synchronized.
ASR is also famous for its cost-efficiency — despite being packed with a set of backup, disaster recovery and reporting features, it will cost less than most of its industry competitors. In a way, Azure Site Recovery is a low-cost alternative to more conventional approaches where the only required expenses are for storage to support the application snapshots, the retention of recovery points and a monthly service fee.
ASR is capable of integration with such business continuity and disaster recovery solutions as Oracle Data Guard and SQL Always On. From the workload and application protection standpoint, Site Recovery easily integrates with numerous workloads, including DNS, Exchange, Active Directory, SAP, etc.
As we already said, a recovery point objective (RPO) and a recovery time objective (RTO) are critical properties of any disaster recovery solution, and this is what ASR is good at — for most virtual machines an RPO threshold doesn’t exceed 30 seconds, and for some of them replication is continuous. As for an RTO, an organization should use Azure Traffic Manager, a DNS-based traffic load balancer that distributes traffic across Azure regions, to reduce it drastically, thus facilitating an eventual recovery process.
On the other hand, there are some drawbacks that should be seriously taken into consideration before deciding on whether to prefer Azure Site Recovery over other disaster recovery solutions.
First and foremost, the Azure disaster recovery solution requires a high level of expertise, which makes it impossible to use it without an in-house or a freelance IT specialist for all but the simplest disaster recovery scenarios.
Another major disadvantage of Azure Site Recovery is the lack of automation — for instance, failover is a completely manual process, which could turn out to be costly without due regard and knowledge.
One more shortcoming that must not be overlooked is that ASR requires additional software to be fully operational and feature-packed. Thus, as already noted, to maintain a low RTO, Azure Traffic Manager should be used. Or, if an organization runs multi-VM configurations, System Center Virtual Machine Manager will be additionally required.
