4 ms·

They're powerful, reliable, and compared to writing software for an equally-sized cluster or distributed system, (once you're in the right mindset) easy to writ

by Kadin 16y ago

They're powerful, reliable, and compared to writing software for an equally-sized cluster or distributed system, (once you're in the right mindset) easy to write for. Or alternately, not to write for -- you can just keep migrating the same ancient COBOL up to newer systems, without ever changing it, and the stuff just keeps ticking. The business case is that they work, and have a great track record. Overall the biggest selling point that I've seen is probably reliability. There's a perception that mainframes are more reliable than commodity-parts systems. In truth I think this is confirmation and sample bias; if you run a business that has a mainframe (very expensive, built for reliability, software has had 20+ years of debugging) and a bunch of servers (inexpensive, cost-optimized, software is constant work-in-progress), it's always going to seem as though the mainframe is unbreakable and everything else is dangerously unreliable. It's as much a mindset issue as an architectural one. So many businesses will pay the premium for mainframes as their "core" systems, and then hang a lot of commodity systems off of it to provide access or interaction with the mainframe data.

thaumaturgy 16y ago
You're exactly right. I worked on a mainframe for a major Bay Area school district during and shortly after high school, as a computer operator and COBOL programmer. I was there for a couple of years; rebooting the mainframe was unheard-of. It never seemed to develop memory leaks, it didn't get more quirky after it had been running for a long time. Since it wasn't accessible to the internet (or even most of the network), it didn't need to have any time spent on it trying to secure it against the latest Windows bug. It never required software updates, other than the ones that we coded ourselves and deployed without having to reboot anything. The database didn't fall over when we ran a payroll job or report cards. But, best of all -- and I love telling this story, because I think it really illustrates something that the techs using all the modern stuff just don't "get" -- it had the best recovery systems I have ever seen, hands down. So, one day there was a power outage. We had backup power systems, but like a lot of data processing departments we were just a couple of overworked people and they hadn't been checked in a while. They didn't last as long as we were expecting and the mainframe kicks off. Around that time, I'd been playing around with Linux and such, and I had some idea of just how ugly things got when a complex operating system powered off in the middle of doing things. I was a little bit stressed out. The other guy, a clean-shaven greybeard, wasn't. When the power came back on, the mainframe booted up -- quickly -- and resumed its operations from pretty much the exact point at which the power had gone out. It didn't miss a beat, none of the data it produced was erroneous. That was in '98 or thereabouts. To say that mainframes are more reliable than the popular alternatives is an understatement. :-)
- JunkDNA 16y ago
  This is interesting. Clearly it's not just the hardware that makes mainframes this fault-tolerant. I'm curious why other platforms haven't appropriated some of the core features and functionality of the mainframe machines? Is it lack of familiarity? Patents? I'd love for one of my database machines to be this reliable.
  - jff 16y ago
    I think there's probably a few factors involved: 1. Writing completely solid, fully debugged software is Not Sexy, which is why Linux is getting shinier and shinier but the software still has bugs. 2. You and I have probably been spoiled by working with Unix. Now, I've never used an IBM mainframe, but I have used VMS, which is definitely more businesslike than Unix. Working with VMS feels like going to the DMV. Imagine how it would feel to be living in a mainframe world, right out of IBM's most conservative, straight-laced era--because I'm gonna bet you wouldn't be able to play as fast and loose if you had mainframe-style fault tolerance.
wmf 16y ago
They're powerful, reliable, and compared to writing software for an equally-sized cluster or distributed system, easy to write for. Of course a big SMP such as System p has the same advantages (plus the greater familiarity of Unix), so in my mind the question stands. Why mainframes?
- maigret 16y ago
  Right, but big System p also plays in a similar class price than a mainframe with Linux. You get similar functionality on an easier platform (Unix), but the architecture and middleware functionalities are similar.

by Kadin 16y ago

thaumaturgy 16y ago

You're exactly right. I worked on a mainframe for a major Bay Area school district during and shortly after high school, as a computer operator and COBOL programmer. I was there for a couple of years; rebooting the mainframe was unheard-of. It never seemed to develop memory leaks, it didn't get more quirky after it had been running for a long time. Since it wasn't accessible to the internet (or even most of the network), it didn't need to have any time spent on it trying to secure it against the latest Windows bug. It never required software updates, other than the ones that we coded ourselves and deployed without having to reboot anything. The database didn't fall over when we ran a payroll job or report cards. But, best of all -- and I love telling this story, because I think it really illustrates something that the techs using all the modern stuff just don't "get" -- it had the best recovery systems I have ever seen, hands down. So, one day there was a power outage. We had backup power systems, but like a lot of data processing departments we were just a couple of overworked people and they hadn't been checked in a while. They didn't last as long as we were expecting and the mainframe kicks off. Around that time, I'd been playing around with Linux and such, and I had some idea of just how ugly things got when a complex operating system powered off in the middle of doing things. I was a little bit stressed out. The other guy, a clean-shaven greybeard, wasn't. When the power came back on, the mainframe booted up -- quickly -- and resumed its operations from pretty much the exact point at which the power had gone out. It didn't miss a beat, none of the data it produced was erroneous. That was in '98 or thereabouts. To say that mainframes are more reliable than the popular alternatives is an understatement. :-)

JunkDNA 16y ago
This is interesting. Clearly it's not just the hardware that makes mainframes this fault-tolerant. I'm curious why other platforms haven't appropriated some of the core features and functionality of the mainframe machines? Is it lack of familiarity? Patents? I'd love for one of my database machines to be this reliable.
- jff 16y ago
  I think there's probably a few factors involved: 1. Writing completely solid, fully debugged software is Not Sexy, which is why Linux is getting shinier and shinier but the software still has bugs. 2. You and I have probably been spoiled by working with Unix. Now, I've never used an IBM mainframe, but I have used VMS, which is definitely more businesslike than Unix. Working with VMS feels like going to the DMV. Imagine how it would feel to be living in a mainframe world, right out of IBM's most conservative, straight-laced era--because I'm gonna bet you wouldn't be able to play as fast and loose if you had mainframe-style fault tolerance.

wmf 16y ago

They're powerful, reliable, and compared to writing software for an equally-sized cluster or distributed system, easy to write for. Of course a big SMP such as System p has the same advantages (plus the greater familiarity of Unix), so in my mind the question stands. Why mainframes?

maigret 16y ago
Right, but big System p also plays in a similar class price than a mainframe with Linux. You get similar functionality on an easier platform (Unix), but the architecture and middleware functionalities are similar.