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What Is Flash Express?

By Destination Z posted Mon December 23, 2019 03:35 PM


Editor’s note: This article is based on content initially published in the SHARE President's Corner blog.

Included in last year’s announcement of the zEnterprise EC12 (zEC12), IBM introduced the optional Flash Express. So, what is Flash Express? It’s all about using solid-state drives (SSDs) to improve the performance of certain mainframe tasks.

The way I see it, a bunch of IBM developers got together one day and thought about which management workloads could best benefit by using fast SSDs as opposed to slower, mechanical direct access storage devices (DASDs). What I think they were looking for were situations where programs become slowed when having to read/write to mechanical disks. And these developers immediately came up with two scenarios where SSDs could significantly improve performance:

1. Paging, and
2. Dump processing


Paging is an activity where code is loaded and then immediately “paged-out” as a workload attempts to reach steady state. Paging-out to mechanical drives takes a lot more time than paging-out to SSDs, because mechanical drives have moving parts and slower read/write speeds than solid state, no-moving-parts SSDs. By using speedy flash drives, it takes the paging subsystem a lot less time to reach steady state as compared with slower mechanical drives.

By reducing the amount of time an OS has to spend in paging activities, enterprises are able to spend more time doing useful work. The time saved can reduce a paging exercise from a minute to a number of seconds—but in mainframe environments where many applications are being swapped out as a business resets from one activity to another, recovering a number of seconds can be a pretty big deal.

For an example of why cutting transition times down is so important, consider the following. Flash Express is particularly useful in helping with workload transitions—for instance, a system running an overnight batch workload might need to shift to online transaction processing at the open of business on a given day. (Banks and financial institutions, such as stock markets, frequently halt batch jobs in the morning to transition to transaction processing and call center support workloads). Further, in the future, Flash Express might be used to speed paging when handling new big data workloads. By speeding up these transitions, enterprises can get more useful work out of their mainframe servers.

Dump Processing

Flash Express will also be used, over time, to speed up supervisor call (SVC) dump processing by reducing latency times. In short, when work needs to be analyzed, it needs to be dumped and pulled in from disk such that a snapshot of an occurrence can be isolated. As was the case in the paging example, SSDs enable data to be processed by the dump more quickly. And, as a result, managers and administrators are able to accomplish management tasks more quickly, leading to faster troubleshooting and better performance.

This, too, might seem to be a mundane use of SSD technology, but to systems administrators (such as a group of administrators in Italy who apparently got very excited by this), speeding up dumps can also be a very big deal. In this case, Flash Express is a big deal because, while the dump is processing, transactions can be stopped.

As for the future of Flash Express, I expect more innovative uses for SSDs in the mainframe to surface. Any workload that can benefit from significantly faster reads and writes is a prime candidate.

Real World Savings

The primary value proposition of Flash Express is that it can improve performance and availability. Some of the early results from real-world test scenarios that have been run by IBM indicate that DB2 can perform significantly better with Flash Express. Upgrading to a zEC12 gives DB2 a substantial performance boost (upwards of 25 percent) for several reasons. Tests are also showing a performance improvement of up to 3 percent can be seen with Flash Express on the zEC12.

In other words, DB2 on the zEC12 can gives users 25 percent more throughput as a base (due in large part to the faster CPU), plus a potential 3 percent additional performance boost from Flash Express, yielding up to a 28 percent improvement in DB2 performance. Better performance means more efficient computing—and more efficient computing means lower cost to compute.

For more on Flash Express, a technical write-up is available in this IBM Redbooks publication (see Appendix C).

Joe Clabby is a 30-plus year veteran of the IT industry with experience in sales, marketing and research/analysis. He currently focuses on consolidation, virtualization and provisioning of IT resources.