By Guest: Philip Merry
Company: SIOS Technology
Show: Data Driven
Topic: Cloud Native
Enterprise IT teams are pouring significant budget into multi-availability zone and multi-region cloud deployments, confident they’re buying protection against downtime and disaster. The geographic distribution feels like insurance—US East goes down, US West takes over. Problem solved, right?
Not quite. And the gaps between what organizations think they’re getting and what they’re actually protected against can be catastrophic.
Philip Merry, Solutions Engineer at SIOS Technology, breaks down the critical vulnerabilities that persist even in multi-region architectures—and why geographic distribution alone doesn’t guarantee seamless application failover.
“A lot of the draw of multi-availability zone or multi-region deployments is to gain some extra protection and risk reduction in the environment,” Merry explains. “And that is provided when using a multi-region deployment, but that doesn’t ensure seamless failover for applications between those regions.”
The problem isn’t the infrastructure—cloud providers deliver multi-region infrastructure resilience effectively. The problem is at the application layer, where two critical failure modes emerge: split-brain conditions and data inconsistency.
A split-brain scenario occurs when both regions believe they’re the active operational copy of the environment. In practical terms, this means your US East database and your US West database both think they’re the source of truth. Both are accepting writes. Neither is replicating to the other. The result: conflicting data, potential corruption, and a nightmare recovery scenario.
“You have to consider the possibility of a split brain, where both systems in either region believe that they are the active operational copy of the environment,” Merry warns. “And so you need a high availability solution that can manage that failover and switchover between those regions and help to avoid those conditions.”
Multi-region deployments don’t inherently prevent split-brain. In fact, they can increase the risk if not managed with application-aware failover orchestration that understands which system should be active and enforces that state across regions.
The second critical gap is data consistency. Geographic distribution introduces latency. Replication takes time. And when failover happens, the secondary region needs the most current data to maintain business continuity.
“If my US West region doesn’t have all the data that my US East region has, it doesn’t do me much good if I can bring the database into service over there, because it doesn’t have the up-to-date data that I need to remain operational,” Merry explains.
This is where recovery point objectives get blown. You’ve failed over to a secondary region, the application is running, but you’re operating on stale data. Transactions are missing. Customer records are out of sync. Your business continuity plan just failed at the data layer.
“Your solution also needs to make sure that your data is replicated and present on the standby systems, so that, in the event that you do need to switch over to another region, you are continuing to operate with up-to-date data, and you’re not losing anything in your recovery point objective,” Merry says.
Multi-region deployments do provide valuable protection against catastrophic infrastructure failures—data center fires, natural disasters, regional outages. That risk reduction is real and worth the investment. But it’s not sufficient for application-level high availability.
“In order to ensure seamless failover, you need to make sure that your prerequisite applications, resources, services, and data are all available,” Merry notes. “That requires application-aware orchestration that understands dependencies, manages data replication, prevents split-brain, and ensures that when failover happens, it happens correctly.”
The bottom line: multi-availability zone and multi-region deployments are necessary but not sufficient. Without application-aware high availability solutions that can orchestrate failover, enforce active/standby roles, and ensure data consistency across regions, you’re still vulnerable to the very downtime scenarios you’re trying to prevent.
