In the world of enterprise IT, downtime is measured in the cost per second. For organizations running mission-critical workloads on IBM i (formerly AS/400, iSeries, System i), the difference between a minor interruption and a catastrophic business failure often comes down to one acronym: GDPS (Geographically Dispersed Parallel Sysplex). However, with the introduction of tighter coupling between operating system releases and storage replication, the threshold known as 2.1 GDPS has become the new gold standard for near-zero Recovery Time Objectives (RTOs) and Recovery Point Objectives (RPOs).
But what exactly is "2.1 GDPS"? It is not simply a software version number. Instead, it refers to the integration of IBM i 7.2 (or later) with Global Mirror (formerly XRC) and Metro Mirror (formerly PPRC) in a GDPS environment, refined by the operational standards defined in the IBM Redpaper REDP-5501, "GDPS V2.1". For the IBM i professional, understanding 2.1 GDPS means understanding how to fuse logical replication with physical storage clustering.
You cannot achieve 2.1 GDPS without IBM DS8000 series storage. These arrays provide the underlying Global Mirror (asynchronous) and Metro Mirror (synchronous) links. The "2.1" spec requires DS8000 LIC (Licensed Internal Code) level 7.8 or higher to support the IBM i-specific command sets.
When architects discuss a "2.1 GDPS solution," they are referring to five distinct technological layers working in concert:
Achieving exactly 2.1% growth requires a mix of demand-side and supply-side factors:
Monetary policy must be calibrated to avoid overheating, while fiscal policy supports structural reforms. For instance, a 2.1% growth rate is often associated with a neutral interest rate environment where central banks neither aggressively tighten nor ease.
2.1 Gbps stands for 2.1 gigabits per second, a measure of data transfer rate. It represents the capacity to transfer 2.1 billion bits of data per second. In the context of internet and networking, this refers to the speed of data transfer.
In the context of IT and industrial automation, particularly within IBM mainframe environments, GDPS refers to a suite of disaster recovery and data mirroring tools. However, when coupled with the numeric prefix "2.1," the technical community is almost universally referring to a specific revision of a metrology or filter standard.
For the purpose of this article (and the intent behind the keyword "2.1 gdps"), we are focusing on the metrology and surface texture standard—specifically the Gaussian filtering standard used in ISO 16610-21.
