Abstract

IBM and Cisco present a joint enterprise storage architecture for IBM z17 mainframe environments that combines IBM DS8000 storage with Cisco MDS FICON directors and switches to deliver interoperability, resilience, and operational continuity in mission-critical data centers. The report emphasizes that organizations can adopt IBM-qualified z17 FICON connectivity while continuing to leverage existing 32G FICON infrastructure, with both 32G and 64G connectivity options available as environments evolve. This approach is intended to reduce migration complexity and avoid a forced 64G SAN upgrade while preserving compatibility with existing SAN investments. 

The solution is built around FICON, IBM’s Fibre Connection protocol, which overlays IBM z/Architecture I/O onto a SAN fabric using directors and switches in a fabric topology. Tolly’s analysis combines lab demonstrations, Cisco and IBM qualification data, and solution documentation to show how the integrated platform supports reliable connectivity between the IBM z17 mainframe and IBM DS8000 storage through Cisco MDS infrastructure. Qualification coverage included roughly 50 tests across six categories: new functionality, unit-level validation, serviceability, mixed workloads, recovery, and regression, with the report stating 100% completion in all areas under Cisco NX-OS 9.4(3b), certified in August 2025. 

A major theme is resilience. Tolly notes that Cisco MDS 9700 Multilayer Directors are designed without a single point of failure, and its testing on Cisco switches and directors running NX-OS 9.4(3b) found that redundant power supply failures caused no traffic disruption; when a PSU was taken offline, traffic continued uninterrupted and the unit recovered automatically when restored. Cisco also cites additional resilience through redundant supervisors, up to six fabric modules, fans, and hot-swappable components. 

Technically, the platform supports qualified Cisco devices including the MDS 9710, 9706, 9220i, and 9148V, with support for 16G, 32G, and selected 64G FICON optics and features such as CUP in-band management, wire-speed ISL encryption, secure boot, port ACLs, VSAN isolation, and power-efficiency enhancements including Transceiver Power Control and Power AutoTune.