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Mirroring Overview

Traditional high availability and data replication solutions often require substantial capital investments in infrastructure, deployment, configuration, software licensing, and planning. InterSystems IRIS® database mirroring is designed to provide an economical solution for rapid, reliable, robust automatic failover between two InterSystems IRIS instances, providing an effective enterprise high-availability solution.

Traditional availability solutions that rely on shared resources (such as shared disk) are often susceptible to a single point of failure with respect to that shared resource. Mirroring reduces that risk by maintaining independent resources on the primary and backup mirror members. Further, by utilizing logical data replication, mirroring avoids the risks associated with physical replication technologies such as SAN-based replication, including out-of-order updates and carry-forward corruption.

Combining distributed caching with mirroring provides an additional level of availability; the application servers in a distributed cache cluster with a mirrored data server treat a mirror failover as a data server restart, allowing processing to continue uninterrupted on the new primary, which greatly diminishes workflow and user disruption. Configuring the two failover mirror members in separate data centers offers additional redundancy and protection from catastrophic events.

In addition to providing an availability solution for unplanned downtime, mirroring offers the flexibility to incorporate planned downtimes (for example, InterSystems IRIS configuration changes, hardware or operating system upgrades, and so on) on a particular InterSystems IRIS system without impacting the overall Service Level Agreements (SLAs) for the organization.

Finally, in addition to the failover members, a mirror can include async members, which can be configured to receive updates from multiple mirrors across the enterprise. This allows a single system to act as a comprehensive enterprise data warehouse, allowing enterprise-wide data mining and business intelligence using InterSystems IRIS Business Intelligence™. An async member can also be configured for disaster recovery (DR) of a single mirror, which allows it to seamlessly take the place of one of the failover members should the need arise. A single mirror can include up to 16 members, so numerous geographically dispersed DR async members can be configured. This model provides a robust framework for distributed data replication, thus ensuring business continuity benefits to the organization; for more information, see Mirror Outage Procedures in this chapter.

This remaining chapters in this book discuss the following topics: