A few years ago I built a presentation on zIIP Capacity Planning. It highlighted the need for better capacity planning for zIIPs and outlined precisely why zIIPs couldn’t be run as busy as general purpose processors (GCPs).
Since then a lot has changed. And I, in common with most people, have a lot more experience of how zIIPs perform in customer installations. So, earlier this year I updated the presentation and broadened the title to include Performance.
I was due to “beta” the presentation at a user group meeting in London in March. Further, I was due to present it to a group of customers in Stockholm in May. The former, understandably, was cancelled. The latter happened as a Webex.
The essential thesis of the presentation is that zIIP Capacity and Performance needs a lot more care than most customers give it, particularly for CPU-stringent consumers such as the Db2 engine (MSTR and DBM1). (Actually I’ve talked about Db2 and it’s relationship with zIIP in Is Db2 Greedy?.)
What’s really new about this presentation is a shift in emphasis towards Performance, though there is plenty on Capacity. And one key aspect is LPAR Design. For example, to aid the “Needs Help” mechanism where a General Purpose Processor (GCP) aids a zIIP, some LPARs might need to forego access to zIIP. This might be controversial – as you want as much zIIP exploitation as possible. But for some LPARs giving them access to zIIP makes little or no sense. Meanwhile other LPARs might need better access to zIIP.
The presentation is also updated in a few key areas:
- More comprehensive and up to date treatment of Db2 – and if you are a Db2 customer you really should pay attention to this one. (I’m grateful to John Campbell and Adrian Burke for their help with this topic.)
- zCX Container Extensions in z/OS 2.4. This can be a major consumer of zIIP. Obviously this needs to be planned for and managed.
- z15 System Recovery Boost (SRB). I’m looking forward to seeing how much this speeds up IPLs – and I think I’m going to have to refurbish my IPL/Restart detection code to do it justice. I also think you will want to consider how an event affects the other LPARs sharing the zIIP pool.
As with So You Don’t Think You’re An Architect?, I’m planning on evolving the presentation over time – and the above list shows how I’ve already done it. I’m also interested in giving it to any audience that wants it. Let me know if it would be of interest and I’ll see what I can do.
In the mean time, here’s the presentation: “zIIP Capacity And Performance” presentation