Never has the phrase "you complete me" been more apropos than for describing the relationship of the new IBM z13s server with the recent delivery of the IBM DS8884 storage system.
(Note: The phrase was made popular by Cameron Crowe’s 1996 film “Jerry McGuire”, featuring Tom Cruise, Cuba Gooding Jr., and Renée Zellweger. Watch this scene from that movie on YouTube if you are too young to remember it: https://www.youtube.com/watch?v=NpWAlvWNZj0 )
The DS8884 complements the z13s by providing a more cost effective entry point for mainframe storage, new and enhanced resiliency features, full architecture compatibility with the full DS8000 family of storage systems, performance optimizations for mainframe and distributed workloads and simplified licensing for advanced functions.
Cost Optimized
The DS8884 storage system is a cost optimized version of IBM's DS8000 enterprise class storage system, the premier storage used by mainframes. Cost reductions come from the use of a standard 19U rack design and by limiting the scale of capacity and connectivity of the storage system. The lower acquisition costs and standard floor space requirements make the DS8884 attractive for the mainframe mid-range market that is also covered by the z13s mainframe. The DS8884 supports all the qualities of service, resilience, advanced functions and data replication features expected by the most demanding clients, for both mainframe (z/OS, z/VM, TPF, VSE and Linux on z Systems) and distributed systems. The DS8884 will have 6-core controllers, up to 256 GB Cache, up to 64 ports that can negotiate between 16Gbps, 8Gbps and 4Gbps, up to 240 drives in a single-rack configuration or 768 drives in a three-frame configuration, and up to 120 flash cards in High Performance Flash Enclosures (HPFEs).
Enhanced Resilience – Self Diagnosing and Self-Healing
Clients require I/O channel, storage system and SAN technology to be self-diagnosing and self-healing. This requirement includes the need to proactively verify the quality of the SAN infrastructure and if failures do occur, quickly identify the failing components. IBM has invented new extensions to the Fibre Channel standards (FC-LS-3) called Read Diagnostic Parameters (RDP) to facilitate this. RDP allows for the z System servers to read critical instrumentation data for each visible link in the SAN (e.g. the channel link, SAN entry port, SAN exit port and DS8000 control unit port). The z13s reads the data and provides it to z/OS for processing (OA49089):
- z/OS provides new operator commands to display critical information about the optical links. Data such as the optical signal strength for both transmit and receive links, temperature, voltage, number of link buffers, capable speed, etc. No longer do the operations staff have to run around the data center with a light meter, inserting and removing it for all the links to verify the quality of the connections. The new LINKINFO parameter on the Display Matrix command for devices supplies the data.
- New z/OS health checks have been added to the health check infrastructure to proactively detect potential SAN issues. The z/OS SAN health checks will use the RDP data to look for inconsistent link speeds from the channel through to the storage systems as well as across all the channels to same storage system. This simplifies diagnosing SAN performance issues and does it proactively. Additionally, a new SAN health check has been added to verify that a sufficient number of buffer-to-buffer credits has been allocated to support the link speed that is capable for the distance that is being used. This too makes SAN performance issues easy to identify and does it proactively.
- The RDP data is also written to SMF records daily. This will allow future analytics to process the data and proactively identify links that are degrading and may be likely to fail.
- The bit error rate was reduce by 300 times. The z13 FICON Express16S channel and the 16Gbps host adapters (HA) in the DS8000 support forward error correction (FEC) technology that allows correcting up to 11 bit errors in a row for each block of 2116 bits. This essentially improves the quality of the link the same amount as if the optical signal strength were doubled. The DS8880 and the z13 SANs are self-healing. This makes the faster link speeds at least as reliable as 8Gbps technology.
- The DS8000 storage systems, z13 and FICON Directors provide self-describing information that allows the software to identify any potential single points of failure in the I/O configuration. This checking can be driven from the SAN health check infrastructure to proactively identify I/O configuration errors that could impact availability:
http://www-03.ibm.com/systems/z/os/zos/features/unix/bpxa1ty2.html
- The DS8880 series supports multi-target Metro Mirror technology to provide up to two synchronous copies of data. In order to greatly simplify the task of defining the I/O configuration in the mainframe, the z13 and z13s provide support for up to four subchannel sets. This makes the definition of the second synchronous copy trivial.
Performance Leadership
The DS8884 and the entire DS8880 series of storage systems provide a number of technologies to deliver industry leading I/O performance for z/OS workloads:
- Reduce DB2 commit times by 40% using 8Gbps links and up to 66% using FICON Express16S channels with DS8884 16Gbps HAs. The zHyperWrite technology allows DB2 clients using IBM Metro Mirror and HyperSwap technology (GDPS or TPC-R) for continuous availability.
- zHyperWrite technology allows DB2 clients using IBM Metro Mirror and HyperSwap technology (GDPS or TPC-R) for continuous availability to reduce DB2 commit times by 40% using 8Gbps links and up to 66% using FICON Express16S channels with DS8884 16Gbps HAs.
- Performance measurements shows a 7% reduction in write I/O service time (512K writes) at machine room distances and up to 68% reduction in I/O service times at 100KM. This enhancement most especially compliments the zHyperWrite capability as well as the cross site I/O that may occur using Geographically Dispersed Parallel Sysplex (GDPS) configurations. The z13 and DS8880 support an enhanced write protocol (zHPF Extended Distance II) that accelerate the execution of large write operations (>64K) by using FICON Express16S and the DS8880 AND 16Gbps host adapters.
- FICON Dynamic Routing (FIDR) is a new feature of the z13s, z13, DS8884 and DS8880 series of storage systems. The z13 has made the changes to the channel subsystem to allow the use of dynamic routing policies in cascaded FICON SANs. Static routing policies use the same routes across the inter switch links (ISLs) for the same I/O systems. This old restriction simplified the FICON firmware implementation but does not allow optimal use of all the ISL bandwidth. A static routing policy is like picking the checkout line at the grocery store before you even arrive. FIDR allows clients to use dynamic routing policies such as Exchange Based Routing (Brocade) or Open Exchange ID Routing (Cisco). Dynamic routing allows clients to reduce costs by sharing the same ISLs for FICON and FCP traffic (Metro Mirror) and drive the ISLs to higher utilizations without incurring queueing delays. This also improves resilience by making the system better able to handle work load spikes.
Conclusion
The DS8884 provides mainframe clients a world class storage offering that has been optimized for the new z13s processor. It provides and attractive cost point for midrange z Systems clients, full architecture compatibility with the DS8880 series of storage systems and all the resilience characteristics and performance features that the most demanding z Systems clients have come to expect from IBM.
References
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