Microsoft has recently announced that Azure will no longer charge for data transfer across availability zones whether using private or public IPs. This change will facilitate the development of resilient multi-AZ applications without the concern of additional data transfer expenses.
The price change from Azure is designed to help customers build more resilient and efficient applications and solutions by deploying on multiple availability zones without incurring additional costs. Among the main benefits of dropping the data transfer fees between availability zones, Azure highlights the ability to enhance application resilience, simplify architecture planning, encourage best practices, and create zonal and zone-redundant services:
By eliminating data transfer fees between availability zones, we make it easier for customers to design and deploy applications that are redundant across multiple availability zones. This can significantly reduce the risk of downtime and ensure higher availability of their services.
Microsoft will still charge for data transfers between Azure regions, with costs varying from $0.02 per GB between regions in the US or within Europe to $0.16 per GB between regions in South America. The cloud provider adds:
We aim to support customers in adopting the best practice architecture for cloud deployment. Removing cross-AZ transfer costs encourages the use of highly available and fault-tolerant system architectures without additional fees.
The change initially took the community by surprise, with some users pointing out that Azure had quietly removed all mention of intra-region cross-AZ charges from its bandwidth pricing, while others noted that Azure had planned to charge for it for many years but never actually did. While cross-AZ data transfer is not charged on Azure, other cloud providers still apply additional costs for that traffic. Dustin Whited, director of security engineering at Aquia, comments:
Microsoft Azure removed cross-AZ data transfer charges. Will Amazon Web Services (AWS) follow? This is a commonly overlooked source of unexpected charges for highly available applications.
On AWS, the data transfer cost between different availability zones in the same region is $0.01 per GB in each direction, very similar to the cost of egress fees. Google Cloud similarly charges for data transfer to a different zone in the same region, with prices comparable to those of AWS. Ari Palo, lead technologist at Alma Media, adds:
I sure hope AWS follows this. Cross-AZ data transfer tax is the most stupid thing ever.
Developers have been finding different ways and creating more complex deployments to reduce the impact on billing, with Corey Quinn, chief cloud economist at The Duckbill Group, writing an article a few years ago claiming that cross-AZ data transfer costs more than AWS says. Amid pressure from European regulators, all three major providers are now ending egress fees for customers exiting the cloud, as reported separately on InfoQ.
