Dell Chassis Management Controller Version 3.0 for Dell EMC PowerEdge VRTX User's Guide

Fault-Tolerance in Storage Controllers

High Availability (HA) in storage enables availability of multiple integrated components and multiple access points to storage resources. In case a storage component stops functioning, the server is supported by a second critical component or path to the available data. High Availability only minimizes downtime by restoring services behind the scenes, in most cases before the non-functionality is visible, but does not eliminate downtime. Fault Tolerance (FT) makes use of redundant components within a storage system, which are configured to behave as backup components and are kept in standby mode. Storage Controllers in fault-tolerant mode prevent disruption of storage services and automatically take over the services of a component that has stopped functioning. Performance remains consistent throughout this failover process since the redundant components(controllers) are not used during normal operating conditions.

Using the fault-tolerant feature of controllers, you can manage the tasks associated with shared storage that are achieved by having an active and passive (peer) controller. Active controller is the controller that is active and monitors all the storage-related processes. Working status of both controllers are communicated between controllers so that when an active controller stops functioning, the passive controller acting as a peer hot-spare, takes over in a seamless manner.