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DS8880 Architected to Evolve.

By Archive User posted Wed May 31, 2017 05:53 PM

The DS8880 storage system has an architecture built to evolve. From the physical infrastructure to the firmware features and functions the DS8000 family has a legacy of evolution. Each generation builds on the features and functions of the prior generation. The DS8880 hybrid and DS8880F all flash systems are the currently available generation.

Data storage solutions in the data center are constantly being developed and refined. The rapid shift from spinning disk to flash will be followed by NVMe protocol implementations and later storage class memories. Within that changing landscape there are some constant critical attributes. The basics being enhanced by these media and infrastructure improvements are:
• Reduced latency
• Increased I/O processing capability
• Higher sequential bandwidth
• Higher capacity arrays
Such radical performance and capacity improvements also highlight the importance of system level robustness. As capabilities increase, more work is being consolidated on a physical system implementation. Consequently the storage system needs to provide reliable and consistent performance in the event of the certainty of eventual component failure. The challenge is to deliver disruptive technology while maintaining reliability and high availability of the storage infrastructure.

Over the years I have heard generalized high-level descriptions of new architectures that offer simple strategies for achieving high performance with resiliency and availability. Often these pitches are followed with the statement “It just works”. At that point in the discussion I generally become skeptical. Reliability, high availability and disaster recovery is hard. The risk is never the scenario that the developers thought of and planned for, it is those pesky nuances that defy the imagination of the development team. The successful product team recognizes this challenge. The DS8000 family has a proven track record of delivery of new technology and innovation while leveraging re-use of the bedrock of prior generation firmware and function.

The DS8880 family excels in a mixed workload environment, serving both mainframe and distributed host access. The DS8880 has three classes of systems (Business class, Enterprise class and Analytic class) that are differentiated by scale of capacity, connectivity and maximum performance. The article “DS8880 All-Flash – A Look under the Hood” (by Jeff Steffan - March 3, 2017 ) gives an excellent summary of the all flash system capabilities. All three classes of system provide the same low latency and support the same replication functions and integration with GDPS Hyperswap and PowerHA to provide industry leading HA and DR capabilities. In addition there is an ever-growing set of features such as new Easy Tier function and channel innovations as well as storage array innovations such as the Gen 2 High Performance Flash Enclosure.

You will be seeing in the months to come more articles detailing the replication capabilities and new functions, so I will not delve too deeply on those. My purpose in this article is to provide an overview of the internal architecture and how it enables integration of new technologies and introduction of new functions while preserving industry leading features, resiliency, high availability and disaster recovery capabilities.

The DS8880 is an amalgam of technology drawn from IBM Storage, Power Systems, and zSystems. The structure of the DS8880 is a three layer architecture with multiple layers of redundancy and failover capability providing better than 5 nines of availability at the individual system level and when in a hyperswap environment better than 6 nines of availability.

At the top of the structure are the host adapters. Currently these are 16Gb/s or 8Gb/s Fiber Channel or Ficon adapters. Each adapter is comprised of protocol chips, a unique ASIC for data formatting and protection as well as a powerful on card four core 2 Ghz processor and memory. The host adapter engines manage the interface protocol and internal data formatting and protection. In cooperation with the control nodes the host adapter engines also manage traffic in and out of the system cache implemented in the control nodes. Each adapter is shared by both Power Server control nodes with redundant data paths enabling smooth failover capability when required.

At the middle of the structure are the control nodes. Currently these are Power 8 servers. Processor configurations range from 6-core in the DS8884 up to 48-core in the analytic model. System memory ranges from 128GB to 2 TB. The control nodes are a shared memory caching structure. Firmware manages the caching algorithms as well as advanced functions such as Easy Tier and replication. The control nodes operate in an active – active configuration to assure continued function in event of a failover. Furthermore, because the I/O processing is distributed across the host adapters, control nodes and the back end RAID engines, there is often little to no perceptible system performance impact for such an event.

At the back end of the structure are the device adapters. Like the host adapter they are powerful I/O management processing engines. There are two types of device adapter. The High Performance Flash controller is purpose built to accelerate and optimize access to Flash arrays. The traditional disk adapter is used in our hybrid configurations to manage the HDD arrays. Like the host adapters the device adapters are comprised of protocol chips, processor engine and IBM unique ASICs for data formatting and data protection as well as RAID array management and acceleration. In particular the Flash array controller ASIC and processor implementation is tailored to optimize flash media performance. As with all other system functions the RAID controllers are in a fully redundant configuration for continued access and rapid failover and recovery when needed.

Using the Power Servers as the control nodes and PCIe as the internal fabric, the DS8880 family is architected to enable innovation at each layer of the system while preserving the proven features and functions from the prior generations. The infrastructure evolution is shown below starting with the DS8300 through the current DS8880.

Over the generations we have enhanced control nodes following the Power Systems technology, introduced new host connectivity, refreshed internal fabric, enhanced the power distribution, made physical footprint improvements and introduced faster storage media.

Looking forward the DS8880 will continue to evolve to provide even higher performance and availability. For a near term example please take a look at Harry Yudenfriend’s post about zHyperlink.
In Jan 2017 IBM issued a statement of direction regarding zHyperlink, an ultra low latency DS8880 / zSystem channel enhancement. The DS8880 has the hardware provisions already in place, once the function is made generally available a firmware update will enable the zHyperlink technology.