zHyperLink: Just Another System z DASD I/O Function Enhancement?

Over the last several decades or so the IBM Mainframe platform has delivered several new technologies that have dramatically improved the performance of disk (DASD) I/O performance.  Specifically the deployment of ESCON as the introduction to Fibre Optical channels, followed by EMIF for channel sharing and reduced I/O protocol, superseded by FICON and most recently zHPF.  All of these technologies have allowed for ever larger amounts of data to be processed by the System z server and the adoption of Geographically Dispersed Parallel Sysplex (GDPS) implementations for business continuity reasons.  Ultimately mission critical data and decisions are facilitated by applications and sub-second response times for these transactions is expected.  Some might say that we’re always running to stand still from a performance perspective when implementing the latest System z technologies?

In reality, today’s 21st Century mission-critical application is not just capturing and storing customer data, it’s doing so much more, attempting to make informed business decisions for a richer customer experience!  Historically a customer transaction would be on a one-to-one basis (E.g. ask for a balance query), whereas today, said transaction might generate more data for the customer, potentially offering them a new or enhanced product.  In theory, this informed and intelligent transaction processing delivers a richer experience for the customer and potentially new revenue opportunities for the business.

For several years IBM have integrated the Cloud, Analytics, Mobile, Social & Security (CAMSS) initiative into their product offerings, recognising that a business transaction can originate from the cloud or a mobile device, potentially via a Social Media platform, require rich processing via real-time analytics, while requiring the highest levels of security.  Of course, one must draw one’s own conclusions, but maintaining sub-second or ultra-fast transaction response times, with this level of CAMSS complexity requires significant performance enhancements.  To deliver such ultra-fast response times requires the DASD I/O subsystem to maintain the highest levels of performance, aligned with the latest System z server platform…

In January 2017 IBM issued a Statement of Direction (SoD) and associated FAQ for their zHyperLink technology.  zHyperLink is a new short distance mainframe link technology designed for up to 10 times lower latency than zHPF.  zHyperLink is intended to accelerate DB2 for z/OS transaction processing and improve active log throughput.  IBM intends to deliver field upgradable support for zHyperLink on the existing IBM DS8880 storage subsystem.  zHyperLink technology is a new mainframe attach link.  It is the result of collaboration between DB2 for z/OS, the z/OS operating System, IBM System z servers and the DS8880 storage subsystem to deliver extreme low latency I/O access for DB2 for z/OS applications.  zHyperLink technology is intended to complement FICON technology, accelerating those I/O requests that are typically used for transaction processing.  These links are point-to-point connections between the System z CEC and the storage system and are limited to 150 meter distances.  These links do not impact the z Architecture 8 channel path limit.

From a DB2 I/O service performance perspective viewpoint, at short distances, a native FICON or zHPF originated I/O typically requires 300 Microseconds (μs) for a simple I/O operation.  The coupling facility for z Systems typically can read or write 4K of data in in under 8 Microseconds.  zHyperLink technology will provide a new short distance link from the mainframe to storage to read and write data up to 10 times faster than FICON or zHPF; reducing DB2 I/O service times to an anticipated 20-30 Microseconds.

In conclusion, with a promise of 10 times faster processing, as per its fibre optic channel technology predecessors, particularly EMIF and zHPF, zHyperLink is a revolutionary DASD I/O function and not just another DASD I/O subsystem function enhancement.  At this stage, the deployment of zHyperLink functionality is restricted to DB2 and the IBM DS8880 storage subsystem, while we eagerly await compatibility support from EMC and HDS accordingly.  Moreover, as per the evolution of zHPF, we hope for the inclusion of other I/O workloads to benefit from this paradigm changing I/O response time technology.

Finally, as always, the realm of possibility always exists for each and every System z DASD I/O subsystem to be monitored and tuned on a proactive and 24*7*365 basis.  Although all of this DASD I/O performance data has always been and still is captured by RMF (CMF) data, intelligent processing of this data requires an ever evolving Performance Management process and arguably an intelligent software solution (E.g. IntelliMagic Direction Disk Magic or Technical Storage Easy Analyze Disk Mainframe) to provide meaningful information and business decisions from ever increasing amounts of RMF (CMF) data.  In November 2016 ago I delivered the DASD I/O Performance Management Is Easy? session at the UK GSE Annual 2016 meeting accordingly…

FICON (Fibre Connection Channel): 15 Years of Mainframe I/O Improvements

In 1998, IBM introduced FICON channels for enhanced I/O connectivity and performance for their 9672 G5 processors, delivering significant capability when compared to its predecessor, ESCON.  Let’s not forget that ESCON (Enterprise Systems – S/390) was the first iteration of Fibre Channel for the IBM Mainframe, delivering significant capability, when compared with the previous technology of heavy, large and costly copper based bus & tag parallel (S/370) channels.

ESCON channels were first introduced in the early 1990’s, but after less than a decade, the data and associated storage device explosion was exposing the technical capabilities of ESCON, for example:

  • Mainframe Server Channel Support: One IBM Mainframe processor could only support 256 ESCON channels, whereas FICON was offering a ~5-8:1 reduction in channel requirements.  Put another way, a customer could expect to consolidate the number of channels required from ~200 ESCON to ~30-40 FICON.
  • Device Support: One ESCON channel could support up to 1024 devices (sub-channel/device numbers), channel, whereas a 9672 FICON channel increased support by 16 fold, up to 16,384 (16 K) devices.
  • Distance: The performance of ESCON dropped off significantly when the distance between the channel and associated Control Unit was greater than ~9 KM.  FICON increased this distance separation to ~100 KM, paving the way for the Geographically Dispersed Parallel Sysplex (GDPS) topologies we take for granted today.
  • Performance: ESCON performance was limited to 17 MB/S, whereas the first evolution of FICON channels delivered 100 MB/S full-duplex performance.

Clearly the first iteration of FICON technology delivered significant benefit to the IBM Mainframe User, and arguably is the primary Mainframe evolution that has sustained data growth and the adoption of Disaster Recovery and Business Continuity resiliency.  So, what does FICON offer today, some 15 years later?

Just as FICON superseded ESCON, FICON Express has now superseded FICON, offering a technology base that can continue to deliver benefit for many years to come.  FICON Express continues the tradition of offering more capabilities with each new generation of FICON channel.  The features were designed with the future in mind, while remembering the past, by supporting the data serving leadership of System z and enabling improved data access using High Performance functions (I.E. zHPF), while providing backwards compatibility, being able to auto-negotiate the link data rates of 2, 4 or 8 Gbps, namely the various FICON Expressn iterations (2/4/8).

High Performance FICON for System z (zHPF) is a data transfer protocol that is optionally deployed for accessing data from IBM Mainframe compatible storage subsystems (E.g. IBM DS8000, EMC Symmetrix V-Max, HDS USP, et al) and other subsystems.  Initially the data types supported were DB2, PDSE, VSAM, zFS and Extended Format SAM, and more latterly, legacy access methods including QSAM, BPAM and BSAM are now supported.  zHPF leverages the potential of FICON channels to deliver significant performance enhancements, and can help reduce the infrastructure costs for System z I/O by efficiently utilizing I/O resources, minimizing CHPID (Channels), Fiber (Cables), Switch Ports (E.g. Cisco, Brocade) and Control Unit (E.g. Disk Subsystem) resource requirements.  zHPF also compliments the Extended Address Volumes (EAV) strategy for growth, increasing I/O rate capability as the associated disk volume size increases.

The latest generation FICON Express8S channel has two possible modes of operation designed for connectivity to servers, switches/directors, disks, tapes and printers:

  1. CHPID Type FC: FICON, zHPF, and channel-to-channel (CTC) traffic for the z/OS, z/VM, z/VSE, z/TPF, and Linux on System z environments
  2. CHPID Type FCP: Fibre Channel Protocol (FCP) for attachment to SCSI devices for the z/VM, z/VSE, and Linux on System z environments

With FCP channel full fabric support, multiple switches/directors can be placed between the System z server and SCSI device, allowing many “hops” through a storage area network (SAN) and providing improved utilization of intersite-connected resources and infrastructure.  This may help to provide more choices for storage solutions or the ability to use existing storage devices and can help facilitate the consolidation of Distributed Systems servers (E.g. UNIX, Wintel) onto System z servers, protecting investments in SCSI-based storage.

I/O performance improvement rates for the initial iterations of FICON when compared to ESCON and then FICON Express when compared to FICON, and more latterly zHPF have been significant.  Using like-for-like benchmark performance studies, we can see significant performance improvements:

I/O Driver @ 4K Block Size – ~ I/Os Per Second

Channel Type

#I/Os per Sec

n:1 Increase

ESCON

1200

N/A

FICON Express
2/4 Native

14000

11.7

FICON Express
2/4 zHPF

31000

2.3

FICON Express
8 Native

20000

1.5

FICON Express
8 zHPF

52000

2.6

FICON Express
8S Native

23000

1.2

FICON Express
8S zHPF

92000

1.8

NB. Maximum performance is server related (E.g. z10, z114, z196, zEC2).

Compared to ESCON, the latest 8 Gbps FICON channel leveraging from zHPF function delivers ~76 times more I/O throughput compared to ESCON, while significantly increasing throughput, by at least 50% from generation to generation.

I/O Driver Mixed Read/Write – ~ MBs Per Second

Channel Type

#MBs per Sec

n:1 Increase

ESCON

12

N/A

FICON Express
4 Native

350

29.2

FICON Express
4 zHPF

620

1.8

FICON Express
8 Native

620

1.8

FICON Express
8 zHPF

770

1.3

FICON Express
8S Native

620

1.0

FICON Express
8S zHPF

1600

2.1

NB. Maximum performance is server related (E.g. z10, z114, z196, zEC2).

Compared to ESCON, the latest 8 Gbps FICON channel leveraging from zHPF function delivers ~133 times more I/O throughput compared to ESCON, while significantly increasing throughput, by at least 100% from generation to generation.

Once again, the backwards compatibility capability of the IBM Mainframe server is highlighted by the evolution of the FICON channel, and in particular, Disk Subsystems IHV’s, obviously IBM themselves, but notably EMC, HDS and Oracle (StorageTek) in evolving their offering to support the latest FICON technologies.

We sometimes might take for granted how much data can be stored by a single footprint IBM Mainframe and how much performance and throughput capability is available to process this data.  However, we shouldn’t under estimate what role FICON has played in allowing this significant data (I/O) processing capability to grow, often rapidly, sometimes exponentially.

If there is a downside, such performance attributes might have eradicated the skills required to tune I/O subsystems, but that’s perhaps a subject matter for another day…