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New zHPF Protocols Offer up to a 68 Percent Reduction in I/O Service Time for Write Operations



Editor’s note: This is part two of a two-part series on the IBM DS8870 storage subsystem on the IBM z13 platform. Read part one in the July/August 2015 issue.

The IBM z13* system and IBM DS8870 storage subsystem have been designed to deliver on a set of enhancements to meet the ever-increasing demands of transaction processing and cloud, analytics, mobile, social and security. Clients have expressed the desire to share inter-switch links (ISLs) between their FICON* I/O traffic and the Fibre Channel Protocol (FCP) Metro Mirror traffic generated from it. This would allow them to not only share the same physical ports and fibers between switches and sites, but also get predictable and repeatable performance with a dynamic routing policy that was lacking with the older static-based routing policies.

Both of these attributes would save client money by allowing the reduction in port counts, fibers and the leasing of dark fiber bandwidth between sites. Additionally, the people cost for managing the storage-area network (SAN) fiber performance could also be reduced.

With the z13 system, FICON is no longer restricted to the use of static SAN routing policies for cascading FICON directors. This z13 feature that supports dynamic routing in the SAN is called FICON Dynamic Routing (FIDR). It provides the support needed to handle the out-of-order conditions that could occur when using dynamic routing policies in the SAN, thus eliminating any possible protocol errors that used to occur if SAN dynamic routing was enabled. Only qualified FICON directors are supported for use with FIDR. Clients are encouraged to check with their SAN provider to make sure the equipment and firmware versions have been qualified.

The DS8870 storage subsystem has been qualified to work with the FIDR feature and participate in z/OS* health checks to validate that the configuration is supported by all of the attached equipment.

The capability for z Systems* clients to share their fibre channel SANs between FICON traffic and their FCP Metro Mirror traffic can reduce costs. The inability to share ISLs with different routing policies increases costs because it requires additional expense for:

  • Physical hardware including switches, switch ports and ISL links
  • ISL links, which require clients to lease additional dark fibre and bandwidth between sites
  • Personnel and skills to manage the complexity, problem determination, identification of hot spots, instrumentation and accounting

Even in a FICON-only environment, FIDR and SAN dynamic routing policies enable a better balance of the workload over links with predictable and repeatable performance, which will also reduce costs by simplifying management.

Christopher Colonna is the FICON channel firmware execution team lead for z Systems, IBM Systems.

Roger G. Hathorn is a Senior Technical Staff Member for enterprise storage I/O architecture and development, IBM Systems.

Harry M. Yudenfriend is an IBM Fellow with Systems and Technology Group, System z and Power who joined IBM in 1980. He was named an IBM Master Inventor in 2001 and has achieved his 33rd invention plateau.



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