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From: John Levine <johnl@taugh.com>
Newsgroups: comp.arch
Subject: Re: architectural goals, Byte Addressability And Beyond
Date: Thu, 6 Jun 2024 11:55:22 -0000 (UTC)
Organization: Taughannock Networks
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According to George Neuner  <gneuner2@comcast.net>:
>>Consider the equivalent number of mainframes, with their inbuilt 
>>diagnostics capabilities etc, to match that reliability.
>
>Can't find it now and don't remember many details, but ...
>
>A long time ago, there was a story going around about Microsoft vs IBM
>regarding the day-to-day operation of their company web sites.  It
>claimed that Microsoft was running a ~1000 machine server farm with a
>crew of ~100, whereas IBM was running 3 mainframes with a crew of ~10.

It depends on what you want to do.

If you're doing something that is mostly read-only and easy to
parallelize, then it makes sense to use a farm of cheap PCs. But if
you are a bank or an airline, you need to be able to lock your
database so that you debit a bank account or sell a plane seat exactly
once.  There is a rule of thumb that the cost of locking something
grows roughly as the square of the number of things contending for
the lock.

For example, airline reservation systems are the classic example of a
mainframe database. About 25 years ago, ITA Software had the bright
idea to do searches for seats and prices on racks of cheap PCs, which
worked great since it's read only, and if they suggest a seat or fare
that turns out to have just sold out, too bad, try again. But when
travel agents and airlines used it, they kept the ticketing info in a
regular database because it has to work.

-- 
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly