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Microsoft Previews Proximity Placement Groups for Azure-Hosted Apps

• By Kurt Mackie
• 07/15/2019

Microsoft on Monday announced a preview of Proximity Placement Groups, which add assurances that networking latencies won't be an issue for organizations managing complex applications across Azure infrastructure.

It might seem that simply using Azure Infrastructure as a Service (IaaS) would be enough for organizations, given its ability to scale to meet demands. However, organizations running so-called "multitier" applications, with moving parts needing coordination, may need greater control. In short, they may need their operations to happen within the same Azure datacenter to avoid possible service delays.

The new Proximity Placement Groups preview makes sure that the virtual machines (VMs) used by an organization run in the same Azure datacenter to reduce potential latency issues. Here's how Microsoft described it:

Azure proximity placement groups represent a new logical grouping capability for your Azure Virtual Machines, which in turn is used as a deployment constraint when selecting where to place your virtual machines. In fact, when you assign your virtual machines to a proximity placement group, the virtual machines are placed in the same data center, resulting in lower and deterministic latency for your applications.

An early participant in the Proximity Placement Groups preview was SAP, which discovered late last year that latency in various Azure regions sometimes "was not as expected and not in the optimal range" for its HANA VM replication operations. Using the Proximity Placement Groups preview reduced the latency to "less than 0.3 ms between all system components, which is more than sufficient to ensure great system performance," explained Ventsislav Ivanov, development architect at SAP, per Microsoft's announcement.

Microsoft recommends using Proximity Placement Groups for organizations with "multi-tiered, IaaS-based deployments where application tiers are deployed using multiple virtual machines, availability sets and/or virtual machine scale sets."

Microsoft defines an Availability Set as "a logical grouping capability for isolating VM resources from each other when they're deployed," ensuring that those resources run "across multiple physical servers, compute racks, storage units and network switches." Virtual Machine Scale Sets, on the other hand, represent a management capability for identical load-balanced VMs that can be used to provide high availability for hosted applications, according to this Microsoft definition.

Microsoft also has Azure Availability Zones, which are football field-sized datacenters adjacent to Azure regions that add resiliency and fault isolation for Azure workloads. It would seem that using Availability Zones would be sufficient to protect Azure-hosted application workloads. However, performance can still be affected when those workloads expand.

"As the Azure footprint grows, a single availability zone may span multiple physical data centers resulting in network latency that can impact your overall application performance," Microsoft's announcement explained.

It seems that Proximity Placement Groups aims to address these kinds of scalability issues for organization using Azure IaaS for their applications. However their use also imposes a "deployment constraint" on organizations because organizations can't use VMs outside the datacenter automatically selected by the Proximity Placement Groups feature, Microsoft's announcement explained.

How VMs get deployed with the Proximity Placement Groups feature depends on an organization's needs, which may be either to reduce latency or to add resiliency, per this Microsoft document:

If latency is your first priority, put VMs in a proximity placement group and the entire solution in an availability zone. But, if resiliency is your top priority, spread your instances across multiple availability zones (a single proximity placement group cannot span zones).

It's possible to set up Proximity Placement Groups using PowerShell or the command-line interface. The preview is free to use, but there's no service-level agreement and it's not ready for production workloads yet. The Proximity Placement Groups preview is currently available in all Azure regions except "Japan East, Australia East and India Central," according to the document.