Mainframe as a service: Myth Buster 004 - HASSEM PRAG
Myth003 - Mainframes are secure and have advanced features. Mainframe security has advanced so myth not busted.
Mo, Hassem, Mohammed, IT, CIO, Fintech, Advisory, Consulting, Leadership, Technology, Tech, IT, ISFAP,Jay Prag,Farieda Mayet,Jayesh,Bank Zero
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Mainframe Myth Busters: All I/O subsystems are the same so why bother?

We have been asked many times why we should bother worrying about I/O sub-systems and why should we really understand them. Leave it to the disk technology manufacturers and everything will magically heal itself. So we being curious cats and extremely technical decided to perform some tests. We used a cloud approach to distinguish between a mainframe and non-mainframe(x86 architecture). The key aspects of measuring an I/O system is to determine how the instructions are built to fetch data from the database. I am talking machine level instructions here. I am also talking about whether the CPU does the I/O and waits for the I/O to complete or is the I/O performed outside the CPU. This is where the mainframe and x86 architectures are worlds apart. Many disk manufacturers will argue that the disk technology will cope under any architecture and would be the same.

Our results have shown the following:  

  • A thread doing an I/O if not interrupted will continue using the CPU on a x86 architecture, thereby so called hogging the CPU.
  • A thread doing and I/O if interrupted will cause a bottleneck on other workloads, with higher priority workloads compromising other workloads. This becomes a serious issue if you are managing different workloads and can impact customer experiences. Scalability becomes a major issue as you now need additional servers to manage scale.
  • On a mainframe the I/O is offloaded to the SAS processors(separate I/O processors) and the CPU can process workloads whilst the SAS processors can handle I/Os independently of each other. This has shown the best scalability view and workloads are not impacted no matter the type of workload.

In running these tests we have common disk technology, common workloads and common databases. We used Katalon to run scripts with workloads that are identical.

So we believe the myth is busted. You must ensure you have a detailed understanding of your I/O sub-system to ensure you have workload that is scalable with response times that are guaranteed.

 Come chat to us on how we can help.

So we believe the myth is busted.