The Geometry of Redundancy: Why Physically Separate Storage Paths Behave as One System

Abstract

Nowadays,​storage systems are, in most cases, based on the redundancy concept so that physically separate paths, controllers, and devices are considered to produce fault isolation and independent behavior by default. However, in reality, such systems often have failure patterns that are tightly coupled, performance bottlenecks, and recovery behaviors contradicting the physical separation that is visible. This paper reveals that there is a large distance between the storage design perception of redundancy and the systemic behavior witnessed in real-life environments. Therefore, it is argued that redundancy is more of a geometry than a function in most cases. We discuss geometric redundancy, meaning that components are placed in different physical or logical paths, but they are still limited by a common control plane, synchronization mechanisms, queuing dynamics, or workload characteristics, and hence, they behave like one system when being stressed. Though there have been plenty of observations of cascading failures and correlated performance degradation, few have formally analyzed why physically independent paths in storage fail together at the end of the day. In this paper, a method is described that involves architectural decomposition, failure-mode mapping, and workload-driven stress analysis to locate those coupling points that are hidden between different layers of the storage system. The study extends to a real-life example of an enterprise storage environment with dual-fabric connectivity and redundant controllers, where empirical data showed that latency spikes were synchronized, failover was coordinated, and recovery thresholds were shared even though the physical separation was complete. The main points indicate that the efficiency of redundancy depends more on control symmetry, feedback loops, and shared operational geometry than on the physical topology of the system.