Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> http://fosspatents.blogspot.com/2010/08/western-civilization-runs-on-mainframe.html
> 
>   I think the article makes it a bit unclear what "mainframe" means.

There isn't a concise or precise definition:
Mainframes are enterprise level (expensive reliable) machines that are 
optimised for running large transactional workloads (more optimised for 
processing huge amounts of data than performing complex calculations).
They have an obsession for backwards compatibility and most (~95%) 
mainframes are IBM machines running an operating system based on the 40 
year old System/370 and are backwards compatible with System/360.

> What are you going to replace
> them with? A PC (which would go down immediately when its PSU dies or its
> HD gets a bad sector)? Why would that be a good thing?

There are many PC based servers running *nix/Windows with redundant hot 
swappable, power supplies, hard disks (ideally with battery backed 
cache) and fans. These have pretty good reliability but are not 
mainframes. They generally can't cope with CPU/Memory or board failures.

If you really care about availability you can run multiple redundant 
servers (on different sites) or use a proper transactional system.

The thought was that it'd be cheaper to use several smaller cheaper less 
proprietary machines to achieve what had previously been done with one 
big mainframe. IBM would say it is cheaper and simpler to just run one 
big expandable system, than lots of little systems.

The question raised by this story is why is IBM trying to squash 
Hercules? Mainframes and their software provide a huge proportion of 
IBM's revenue. One of the biggest problems IBM has with its mainframe 
business is there are skill shortages, as few people know how to use 
mainframes or have access to learn about them. An emulator would help 
people get these skills but no-one would get very far trying to replace 
a mainframe running on their laptop.

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