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>I read this wonderful article on mainframe OSes. As irony, the url link points to an article mentioning the Unisys mainframe. Unisys later switched to running

by jasode 4y ago

>I read this wonderful article on mainframe OSes. As irony, the url link points to an article mentioning the Unisys mainframe. Unisys later switched to running on commodity x86 servers with a Unisys emulation on top: https://www.google.com/search?q=unisys+clearpath+shift+xeon https://www.google.com/search?q=unisys+clearpath+shift+xeon >, and that you don’t need all the fancy scaling infrastructure because one modern box [mainframe] can support a million concurrent users no problem, and a few such boxes can support tens of hundreds of millions of them, all in something in the corner of one room, with an uptime of decades and no need for any cloud. But it’s hard to do it that way, The author proposes that "mainframes-are-superior" by vague generalizations and no performance data. As a case study, consider that the Sabre travel reservations was the first IBM mainframe commercial customer since 1960. With 6 decades of experience with IBM 360 and Z upgrades, they'd know more about running mission-critical performance workloads on mainframes than just about anyone. And yet, they've been migrating off of mainframes to AWS + Azure + Google cloud : https://www.google.com/search?q=sabre+migration+multi-cloud+google https://www.google.com/search?q=sabre+migration+multi-cloud+... To think of the opposite case from Sabre, let's consider a new YC startup today with no legacy IT systems. Thinking from first principles (i.e. raw math of cpu & io performance & costs on an Excel spreadsheet), what situation makes sense to build the solution on an a new IBM z16 mainframe instead of cloud? If one is an old bank already running an older IBM z14 or z15 mainframe and wants the next iteration of performance improvements, a z16 upgrade is the simplest so probably makes the most financial sense. But without a "legacy IT" constraint, what's the compelling spreadsheet model for a YC company to choose a mainframe?

dangus 4y ago
Also, supporting a lot of concurrent users is easier when the capabilities of the services being offered are very basic. Banks weren't doing things like providing millions of customers instant OCR processing of checks in the mainframe days.
mhh__ 4y ago
Migrating away from mainframes can also be just because of talent availability but also lock in. Where I work we have processes that would make perfect sense chucking jobs at a mainframe (if we implement our language on it...), but IBM have no competition so it's super risky.
neverartful 4y ago
"But without a "legacy IT" constraint, what's the compelling spreadsheet model for a YC company to choose a mainframe?" The most compelling reasons for the mainframe, based on its intrinsic values, are 'RAS' (reliability, availability, serviceability). However, those virtues come with a very high price tag. So far the most part, I cannot imagine any startup business choosing one (UNLESS system downtime will kill the business).
- derefr 4y ago
  Plus, you can squeeze out those same RAS factors from a cluster of commodity x86 boxen, at the software level, if your devs are willing to learn a little Erlang.
rbanffy 4y ago
> Unisys later switched to running on commodity x86 servers It runs the same OS on an emulation layer. Not sure they do it, but you can get zero downtime out of multiple x86 boxes with a number of interesting tricks while pretending you are on a single CPU
derefr 4y ago
> raw math of cpu & io performance & costs on an Excel spreadsheet But that's not the raw math; the raw math is "total OpEx", and OpEx for these large systems is increasingly dominated not by the systems themselves, but rather by development-talent acquisition costs, and operational-maintenance talent labor costs. Even Sabre's choice wasn't "upgrade to z16 vs. move to IaaS"; it was "hire people to replace churned devs+ops to write the next feature of the system: people with z/OS experience, or people with IaaS experience?"
no_identd 4y ago
>And yet, they've been migrating off of mainframes to AWS + Azure + Google cloud Well, kinda: https://techcrunch.com/2021/11/19/why-sabre-is-betting-against-multi-cloud/ https://techcrunch.com/2021/11/19/why-sabre-is-betting-again...

by jasode 4y ago

dangus 4y ago

Also, supporting a lot of concurrent users is easier when the capabilities of the services being offered are very basic. Banks weren't doing things like providing millions of customers instant OCR processing of checks in the mainframe days.

mhh__ 4y ago

Migrating away from mainframes can also be just because of talent availability but also lock in. Where I work we have processes that would make perfect sense chucking jobs at a mainframe (if we implement our language on it...), but IBM have no competition so it's super risky.

neverartful 4y ago

"But without a "legacy IT" constraint, what's the compelling spreadsheet model for a YC company to choose a mainframe?" The most compelling reasons for the mainframe, based on its intrinsic values, are 'RAS' (reliability, availability, serviceability). However, those virtues come with a very high price tag. So far the most part, I cannot imagine any startup business choosing one (UNLESS system downtime will kill the business).

derefr 4y ago
Plus, you can squeeze out those same RAS factors from a cluster of commodity x86 boxen, at the software level, if your devs are willing to learn a little Erlang.

rbanffy 4y ago

> Unisys later switched to running on commodity x86 servers It runs the same OS on an emulation layer. Not sure they do it, but you can get zero downtime out of multiple x86 boxes with a number of interesting tricks while pretending you are on a single CPU

derefr 4y ago

> raw math of cpu & io performance & costs on an Excel spreadsheet But that's not the raw math; the raw math is "total OpEx", and OpEx for these large systems is increasingly dominated not by the systems themselves, but rather by development-talent acquisition costs, and operational-maintenance talent labor costs. Even Sabre's choice wasn't "upgrade to z16 vs. move to IaaS"; it was "hire people to replace churned devs+ops to write the next feature of the system: people with z/OS experience, or people with IaaS experience?"

no_identd 4y ago

>And yet, they've been migrating off of mainframes to AWS + Azure + Google cloud Well, kinda: https://techcrunch.com/2021/11/19/why-sabre-is-betting-against-multi-cloud/ https://techcrunch.com/2021/11/19/why-sabre-is-betting-again...