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hen a system needs to scale, very different types of problems need to be solved. Let us first consider scaling with respect to size. If more users or resources need to be supported, we are often confronted with the limitations of centralized services, data, and algorithms (see Fig. 1-3). For example, many services are centralized in the sense that they are implemented by means of only a single server running on a specific machine in the distributed system. The problem with this scheme is obvious: the server can become a bottleneck as the number of users and applications grows. Even if we have virtually unlimited processing and storage capacity, communication with that server will eventually prohibit further growth

What I have tried:

Can you please explain the bold part?
Posted
Updated 12-May-20 16:33pm
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Solution 1

Think about it: I have information you want, and I am sending it to you right now.
But ... you don't receive it instantly - it takes time to type, then I send it via broadband to New York, which sends it to Toronto, where it reaches CP's servers, which decides to send you an email, so that goes to your email server, and finally your systems check for emails and you get this.

I have vastly more processing power than required to type this - heck, I'm also watching the TV News and talking to Herself while I type. CP's servers have more capacity than needed, your phone, lappie, tablet, or desktop can do many things simultaneously while handling your email.

You can upgrade the processors, memory, and HDD of every single computer in the chain - but it will have no significant effect at all on how long it takes you to get a reply!
The communications channel and it's limitations have the only significant effect on the time it takes.
   
Comments
Tara11 23-Jun-19 14:28pm
   
Sorry, I don't understand how this answer my question. What I need help about is:
The text says even if we have virtually unlimited processing and storage capacity, communication with that server will eventually prohibit further growth.
I think if we have unlimited processing and storage capacity, communication shouldn't never be prohibited further growth?
OriginalGriff 23-Jun-19 14:42pm
   
How would any increase in processing power or memory have got this reply to you any faster?

Transfer of data is restricted by the limitations of the communications medium: in this case it's down to typing speed and email update timing, but that applies to everything. Every form of communications has a transfer rate, a bandwidth - and once that is fully used, it provides a bottleneck: it is not possible to transfer information any faster, even if it can be calculated more quickly.
If nothing else, Einstein says that no information can travel faster than the speed of light (quantum mechanics and entanglement may change that, but we certainly can't use that if it does work).

And all processing is limited by communications: processors already run far, far faster than they can communicate with their own RAM - which is why you have multilevel caches so processors can continue without having to wait for the RAM to "catch up". That's why HDD's have built in caches, because it takes so long to read and write to physical disks.

Make sense?
Tara11 23-Jun-19 15:37pm
   
Yes,makes sense. Thank you so much!
OriginalGriff 23-Jun-19 16:21pm
   
You're welcome!
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Solution 2

One can only pump so much with a fixed diameter hose (i.e. bandwidth is finite).
   
Comments
Tara11 23-Jun-19 15:38pm
   
Thank you so much!
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Solution 4

Solution 3:
Sorry, but doesn't
we have virtually unlimited processing and storage capacity
mean
that we have virtually unlimited bandwidth
Not in the slightest.

Analogy 1 would be having a very large beverage(storage) and a very large mouth(cpu).
The analog to bandwidth would be a beverage straw; a standard soft-drink straw works much better than the tiny straws they put in cocktails.

The second analogy would be automotive.
You can have a very big engine, let's say from a commercial dump truck.
And you can have very big tires, from the same truck.
But if the driveshaft came from a tiny little Fiat; it would twist to the point that it shears in two if you tried to go full throttle

Analogy number 3 will be highways. You can have a 2 lane highway and do 150km/h easily at 3am when nobody else is around.
That same highway during the morning rush hour can be packed with all sorts of commuters, and you will be lucky if you can go 50km/h
   
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Solution 3

Sorry, but doesn't
we have virtually unlimited processing and storage capacity
"mean that we have virtually unlimited bandwidth and ... so we shouldn't have those problems that you said?
   
Comments
RickZeeland 24-Jun-19 2:58am
   
They are talking about having only one server, if you have more than one server then the problem could be solved (but not easily).
Tara11 24-Jun-19 5:41am
   
Thank you so much!
But I didn't mean to have more than one server. I meant one server with unlimited bandwidth, processing,storage capacity,...
In that case we shouldn't never be prohibited, right?
RickZeeland 24-Jun-19 10:20am
   
Yes, but the option of unlimited bandwidth was not mentioned in the story to stress the point that bandwidth is something to reckon with.
Tara11 24-Jun-19 10:32am
   
Thank you so much!
Is "unlimited processing and storage capacity" related to what? Isn't it related to bandwidth?
RickZeeland 24-Jun-19 10:48am
   
No, you can have the most powerful processor and fastest disk, but when you have a slow network card that will slow things down having to do with network and internet activity.
Tara11 24-Jun-19 10:56am
   
Thank you so much!

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