Why Do Mainframes Still Exist? What's Inside One? [video] | Hacker News Reader

Why Do Mainframes Still Exist? What's Inside One? [video]

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I think I’ve made this comment before, but there really are some jobs that monolithic big iron does better, particularly in banking where you need guaranteed exactly-once delivery scaled massively to support transaction processing, where re-creating the system with a modern architecture would need multiple times the infrastructure and maintenance. That combined with existing COBOL/Natural codebases that work pretty reliably and are regulator approved gives mainframes an element of inertia that I suspect will outlive even me.

This is what IBM and people living off mainframes tell the world all day long, but I think you'll have trouble showing that mainframe's job can't be replaced by a few hi-end x86 servers under cost.

Inertia, regulators, and company having lots of money to the point they don't care (banks...) explains mainframes. They do the job well, so why bother replacing them if you don't care that they cost more.

> This is what IBM and people living off mainframes tell the world all day long, but I think you'll have trouble showing that mainframe's job can't be replaced by a few hi-end x86 servers under cost.

It's been tried many times before, and it never works out. Whether it's system complexity that can't be replicated, or woes from floating point imprecision, it's a hell of a lot harder than people who haven't dug into it think.

> It's been tried many times before, and it never works out.

Seems to work just fine for Indian banks and the Income Tax Department.

Is the story published anywhere that you know of? I'd be interested in reading more about this

A Majority of large Indian banks use Finacle for their core banking. It's specifically marketed by Infosys as a replacement for legacy mainframe systems and can be deployed on AWS: https://www.infosys.com/services/cloud-cobalt/insights/finac...

Infosys marketing copy for the GST portal talks about leveraging opensource building blocks: https://www.infosys.com/services/application-modernization/c...

My Google-fu is failing me, you might have better luck searching for specifics about Finacle.

Neat, thanks that's a super helpful launch point!

> It's been tried many times before

Can you link some specific example? That may be an interesting read.

Im on mobile at the moment but I'll see if I can find some when I'm back on desktop. The stories I've read were nearly all on HN over the last 10 years, some as articles and some as comments, that came up on threads about cobol (mainframe rarely seems to make it to relevance lol)

For starters they don't suffer from C and C++ related exploits, given the systems languages that were used to write them like PL/S and NEWP, or the business languages being mainly COBOL, RPG and nowadays Java.

That depends on what the customer does, no?

> However, z/OS also implements 64-bit Java, C, C++, and UNIX (Single UNIX Specification) APIs and applications through UNIX System Services – The Open Group certifies z/OS as a compliant UNIX operating system – with UNIX/Linux-style hierarchical HFS[NB 3][NB 4] and zFS file systems. These compatibilities make z/OS capable of running a range of commercial and open source software.[3] z/OS can communicate directly via TCP/IP, including IPv6,[4] and includes standard HTTP servers (one from Lotus, the other Apache-derived) along with other common services such as SSH, FTP, NFS, and CIFS/SMB.

https://en.wikipedia.org/wiki/Z/OS

Although I like the argument that having an OS that does not require use of C is an interesting feature. Then it's really about the quality software platform, more than about the magic hardware.

If the customer decides to bring UNIX into their workloads, well they should not complain afterwards.

IBM still invests in it's mainframes, and you can also run Linux on VMs, if you wanted to start to transition over some things.

You can run an official IBM emulator for only $5,980.00 per user per year[0]. I've never done it, but this[1] guy did.

Or you can run the open source Hercules[2] emulator, but this is limited to Linux, or older IBM operating systems.

[0] https://www.ibm.com/products/z-development-test-environment

[1] https://colinpaice.blog/2020/06/29/getting-z-os-installed-on...

[2] http://www.hercules-390.org/

One of the reason they still exist is that a software written and compiled in late 80s is still running in production environment unchanged since then.

They also have some other cool features like "serverless", low operational overhead, decoupling between cpu and storage.

I thought the big thing was redundancy and correctness, like having 3 processors run every computation and voting, to make sure no one's bank balance is accidentally in error.

I don't think most of the programmers or managers knows about this, they just assume computation is right; and for sure the correctness check of the bank balance is done on the application level.

Well, if it were only to run software written in the 80s, an emulator would do (modern hardware compensating the inefficient execution many times over).

I'm not sure, but I guess under the hood IBM does some emulation to guarantee backward compatibility.

Largely no, actually; modern z/Architecture is a strict superset of the System/360 ISA from the 70's. Every instruction that accesses memory has the original 24-bit address version, a 32-bit version, and a 64-bit version that also uses 64-bit registers. Thus there's no emulation involved; at least, not that's visible to the OS (but who knows what the microcode is doing underneath)

> modern hardware compensating the inefficient execution many times over

That's assuming volumes haven't changed. They had credit cards in 1980 but the volumes have gone up considerably. I'd also guess trading volumes and other financial products as well.

Mainframes still existing don't seem the most weird part. Who doesn't want an ultra-reliable computer after all? Why not use them if your business is so huge and important that you can afford them? To me nuclear power plants controlled by Windows computers seem much more crazy. The thing which actually seems weird about mainframes is them still using EBCDIC.

That's a function of the software and not the hardware. If you run Linux bare metal LPAR (no one does) or as a z/VM guest you'll have ASCII.

ASCII is still used by older systems also. A modern mainframe won't be using only EBCDIC. If regulations change then system upgrades will be needed to cope with that changing environment. But that involves spending money to do them of course.

EBCDIC exists for compatibility with systems much older than ASCII.

I don't like EBCDIC much, but it has valid reasons to exist. It's not like it would be a good choice for new development, nor would even big blue advocate something not Unicode related now I'd imagine.

Times change and we need to change with the times.

Arent mainframes good example of better technology that lost?

It feels like world gave up on reliable hardware and started fixing it on software/multiple hw instances level

I think thats one of the reasons why Sun Microsystems disappeard. They HW was very reliable.

Nope. They made great software, and not so good hardware. They went away because dot-com bubble burst and tech world cancelled orders of the hardware. Also, bad business decisions linking their success with sales of hardware, instead of support for software.

> "Sun is responsible" for the problem, said a project manager at a large European bank that was affected by it. The manager spoke on condition of anonymity. "Their architecture was fundamentally flawed because there was no ECC checking on the cache memory. This is something you get in even the lowliest Intel processor that costs a few dollars," he said in an e-mail message.

https://www.computerworld.com/article/2585204/sun-fixes-serv...

Yep, it's a dinosaur concept nobody with tight budget wants to pay for, unless they already do and money is no object(big Fortune 500 companies).

I'd say instead of good, it's what I call gold plating. Not in the cheap fake not real gold way but in the "sure a gold plated muffler would be better than an aluminum or zink plated one", but is ultimately not the best place to invest that much resource.

> started fixing it on software/multiple hw instances level

Really we just don't care about it.

Things like ecommerce doesn't have the reliability requirements that finance can have. In some cases you can be losing a million dollars a minute, and screwing up can result in the SEC coming to your offices and arresting people. You can't just issue a refund or a gift card to fix the problems.

And instead of dealing with the sharp edges of the CAP theorem you can just buy one big machine that never fails. It is the kind of decision you rationally make when eventual consistency means that you might wind up in prison.

> It is the kind of decision you rationally make when eventual consistency means that you might wind up in prison.

Thanks for this argument. I‘ll put it on my shortlist.

Running a search engine or youtube on a mainframe would be great, it would mean searches, and especially sorting them, would work perfectly every time, where one could be confident that every matching result is indeed shown correctly ranked.

What’s the deal with the microphone-in-face aesthetic of YouTube videos? Is there some sort of appeal other than showing off your gold-plated mic?

Keeping a cardioid or supercardioid mic close to your mouth reduces room reverberation in the audio which makes it listenable. The person in this video is using an RE20, a classic dynamic microphone widely used in radio broadcasting. In fact in this video it's a little further away than usual, so I think he is trying to play it down. As to the gold microphones that some YouTubers are practically making out with, they keep it so very close for the proximity effect which boosts the bass in their voice. The RE20 has a switch to approximate that effect without being so close, which sounds likely to be on in this video. The tacky gold plating on cheap microphones is not worth anything. The best microphones are grey or black, but you might see a little bit of the gold-plated condenser through the grille.

Have you ever watch a podcast? It's the same, but they avoid the awkward shots by rarely looking into the camera.

Dave says he hopes that they don't tip over the mainframes that often. I hope they do frequently subject them to such testing. In a world with hurricanes, earthquakes and other disasters it can be really important that the mainframe just keeps on trucking. The sysadmins might not be around to babysit them all the time, such as during flooding.

I can't stand Dave's garage. There's no garage - he's a Microsoft millionaire who became a youtuber bragging about his empty golden tech life escapades fueled by the well-paying position as a programmer at Microsoft in the past.

Now he made a shallow acolyte video which seems like it should have been a paid marketing by the IBM mainframe division. I hope he got payed well, otherwise Dave is even more self-unaware that I thought. I get this is what Linus Tech Tips would do for a living, but really, a senior programmer with gobs of money is doing this superficial reporting on a what IBM told him on his trip there???

Seriously, this video (and YT comments it has) is a naive uncritical sucker reverberating most of the standard phrases from the mainframe sphere, although admittedly, with nice high-def shots of the machine components. I expected more serious adult commentary, not a teenage boy fan ravings.

Mainframes by IBM are a niche expensive product that is an interesting concept and history, but it is not an "amazing machine" to be put up today. There is no perspective for most young people working on mainframes, they will be phased out eventually. It's a solid product for the captured audience, which is like 2 banks and card payment processors, but that's it.

"Woo, they don't rely on ECC, they have multiple independent modules, because cosmic radiation, so cool" Get real, this is not an important problem, ECC works already, and good software has to account for occassional HW errors anyway.

Mainframes have their uses, and I haven't heard of anyone pushing them outside of financial applications, where mainframes don't offer much value. As for being eventually phased out, so will everything else, even x86 and ARM.

You don't have to like Dave, his "garage", his channel, or his previous employers, but lots of people find his videos interesting.

I agree. But that's a problem. People are easy to impress these days and don't think through what the message actually is.

You make good points but with excessive vitriol.

You might be right. Dave is to blame.

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