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Comment by myrandomcomment | Hacker News Reader

In reading the comments here it is clear that there are some that do not understand the true difference between running a workload on a rack of servers vs a mainframe. In the case of something like a x86 cluster you need something you can chuck. That is not necessarily true in with a mainframe. You run a "job" and it sorts it out for you. You can even walk up to the mainframe and pull out the cpu the job is running on and nothing happens. It keeps working.

Before anyone starts a huge debate on everything I said it wrong, please understand I know it is not exact. This is just a base level set of one of the main structural differences in the HW/OS that everything is derived from.

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> You can even walk up to the mainframe and pull out the cpu the job is running on and nothing happens.

More precisely:

You can even walk up to the mainframe and pull out the cpu the job is running on and you still get your paycheck.

Correction - s/chuck/chunk

I mean that in x86 you design so that the workload has parts, app server, db, web server etc. in order to spread the workload around. This is not really required on a mainframe as you can just run it all in the same instance (you do not have to nor do you really want to).

This is a very SIMPLE view. I am trying to point out that the HW/OS on a mainframe is design for a very different thing then how people today think of "cloud" design.

Thanks for clarifying.

>"I am trying to point out that the HW/OS on a mainframe is design for a very different thing then how people today think of "cloud" design."

Might you or anyone else have any resources you could share this design paradigm? Thanks.

Not really, because it's the same paradigm that cluster software is designed for.

One thing you missed is that most people use better software on clusters than what you described... software that runs "jobs" and fixes up failures.

>"In the case of something like a x86 cluster you need something you can chuck. That is not necessarily true in with a mainframe."

What is meant by "chuck" here? To throw? If so what is the thing thats needs to be chucked exactly in the case of x86 vs mainframe? Thanks.

Likely a typo. Probably meant chunk as in batch processing.

Maybe not. Mainframes have hot-swappable motherboards.

not a typo; when you design for the typical x86 cluster it's a cluster - you expect components to die and you can throw away whole machines (i.e. expect failure). mainframes on the other hand keep chugging along no matter what.

the usual comparison is a cluster of cheap nodes vs a mainframe

Can't you do the same with a Kubernetes cluster?

In terms of component failure handling, there's very little difference nowadays between a cluster of x86 servers running well-written software connected with high performance network and cluster management system vs mainframe - why should there be, since there's no "magical" advantage mainframes have.

Almost all value of mainframe lies in software compatibility. There's no theoretical or practical advantage they have over clusters of x86 servers.

there's still quite a bit of different on the interconnect side + replaceability side

Well besides not requiring you to solve for HA, sync between nodes, etc. Also the fact that the IO on mainframe is MASSIVE and they have their own IO controllers to sort for IO scheduling.

I have worked on, designed and built both type of systems. Distributed systems cloud style are hard and require the software to sort for everything. For the most part the HW/OS on the mainframe just handles it. It is just a different way to build.

Do you think there's any mainframe lessons that don't exist in today's cloud architecture that could actually be applied (obviously software, not hardware)?

The OS of the mainframe is software. The software running the distributed system is software. For the most part, the software running the distributed system just handles it. It's slightly different.

Earnest question: when is it cheaper for a business to use mainframes rather than x86 clusters? If they are easier to develop on (no need to solve distributed problems) even if mainframes have a 1000x upfront cost, they would still likely be cheaper over time due to smaller development budgets? Where am I misunderstanding?

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