I find a great deal of value in reading your posts, Steve. Knowing that you have experience with Amdahl in hardware adds to my respect for your insights.
> On 29 Aug 2023, at 8:35 am, Steve Thompson <ste...@wkyr.net> wrote: > > Back in the day, we worked on RAS. So we put in error detection hardware > (sometimes that was "firmware, or macrocode) and IBM and all our competitors > were doing the same. And the idea was to have redundant power supplies so > that a CE could do maint, and not take down the system. And if possible, > redundant channel paths to a device controller so that you could pull a > channel cable and replace it. > > Today, with IBM, you can add or subtract CPUs while the machine is running. > But, at least with the z15s, you could not add RAM without taking the system > down, as in power it down. > > So that would be a RAS hit, or, cause you to miss your 99.999 target. > > For people who do hardware and to some degree software (O/S stuff), you do > all you can to recover from any problem. I like VM and its ability to see it > is injured and it will IPL itself. But, to keep those SLAs, there is SSI. So > an LPAR can move its workload to another LPAR (PAIRs determined in advance > here) and keep that work running. We did this at a large health insurer so > that we could do VM upgrades with no outages. > > So how you measure that up time depends on the equipment and ability to do > HOT SWAP, and related so you do not take an outage. > > What happens if a WINTEL server running MQ buys the farm? Those inflight > transactions going through that server may time out and have to be re-driven. > Is this considered an outage? Not if you have a second one handling the load > and it takes over. But that one or 10(?) users may see an error message. Does > that count as an outage if the user only loses a few seconds in getting an > answer? Or a Pharmacy getting info? Or an OR getting info on drug > interactions? > > Need some perspective. > > Steve Thompson > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
