Inter-Zone Latencies in Google Cloud: How to Minimize Oracle RAC Interconnect Latency with Multi-Zone Database Clustering

August 12, 2026

When designing a highly available Oracle RAC deployment on Google Cloud, distributing database nodes across multiple zones (a.k.a. Availability Zones or AZs) is one of the most effective ways to protect against infrastructure failures while maintaining continuous database availability. However, not all zone combinations are equal.

FlashGrid has measured network latencies between zones across Google Cloud regions and found that selecting the optimal zone combination can significantly reduce Oracle RAC interconnect latency, improving both performance and storage synchronization efficiency.

Why Zone Selection Matters

Oracle RAC relies heavily on low-latency communication between database nodes. Two key operations are particularly sensitive to network latency:

Oracle Cache Fusion, which transfers memory blocks between RAC instances
Synchronous storage mirroring, used by FlashGrid’s distributed storage architecture

While Google Cloud’s zones within a region are designed to provide low-latency connectivity, the physical distance between zones varies. As a result, some zone combinations offer measurably better performance than others.

For most workloads, inter-zone latency in Google Cloud remains well below 1 millisecond and has minimal impact on application performance. However, for latency-sensitive Oracle RAC environments, selecting the optimal pair of zones is a simple optimization that can improve cluster efficiency without sacrificing availability.

Example: us-east5 Region

For a two-node Oracle RAC deployment, the latency measurements indicate that placing the database nodes in us-east5-a and us-east5-b provides the lowest inter-node latency. The FlashGrid quorum node can then be deployed in us-east5-c, maintaining resilience across three Zones while having no measurable impact on database performance, since quorum traffic is not latency-sensitive.

Selecting Zones During Deployment

Because zone naming in Google Cloud is the same across different accounts, the latency measurements at the end of this article can serve as a starting point for selecting zones for Oracle RAC deployments. However, FlashGrid recommends validating inter-zone latency in your own environment before deploying production workloads. This can be accomplished by launching a virtual machine in each zone within a region and measuring the average network latency between each pair of zones.

When deploying a cluster using the FlashGrid Launcher, the zone (marked as AZ) for each node is selected on the Nodes page. For optimal Oracle RAC performance, choose the two zones with the lowest measured latency for the database nodes and place the FlashGrid quorum node in a third zone to maintain high availability.

Validate in Your Environment

FlashGrid recommends performing your own latency measurements during architecture planning by deploying a virtual machine into each zone and measuring network round-trip times.