[erlang-questions] Why is Erlang what it is?

[Dominic Williams]

Hi Ulf:

>  Major upgrades in very large applications are often difficult to
>  perform using the soft upgrade facilities alone. We tend more and
>  more towards doing redundancy upgrades instead. One reason is that we
>  have to be able to handle that anyway, and if we can do a hitless
>  redundancy upgrade, why bother with lots of other techniques as well?


Can you pinpoint what makes it difficult to use soft upgrade only? 
Wouldn't it be possible to design very large applications with the aim 
that they be completely soft-upgradable?

The reason I ask is that if so, such knowledge would be more widely 
useful (not all systems can afford the redundancy) and one could reverse 
your argument: if we can do soft upgrade well, why bother with 
redundancy upgrades...

Regards,

Dominic Williams
http://www.dominicwilliams.net

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