Scalability vs. Performance

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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 23-Jun-19 6:49am

Tara11

Updated 12-May-20 16:33pm

PIEBALDconsult

v2

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4 solutions

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

Posted 12-May-20 16:34pm

MadMyche

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?

Posted 23-Jun-19 10:27am

Tara11

Updated 23-Jun-19 18:57pm

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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OriginalGriff · Accepted Answer · 2019-06-23T07:48:00

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.

Posted 23-Jun-19 7:48am

OriginalGriff

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!

Gerry Schmitz · Accepted Answer · 2019-06-23T07:51:00

Solution 2

One can only pump so much with a fixed diameter hose (i.e. bandwidth is finite).

Posted 23-Jun-19 7:51am

Gerry Schmitz

Comments

Tara11 23-Jun-19 15:38pm

Thank you so much!