Comments on: Adding Hardware is not Always the Cheapest Option

By: stephan

stephan — Tue, 27 Jul 2010 14:56:48 +0000

@Yuvi: You’re right, it will get harder and harder for software optimizations. There are low hanging fruit for the first 10% but then it gets harder and costs more money, until buying hardware or tuning the OS is cheaper again until tuning software is cheaper again and so on :-)

By: Yuvi

Yuvi — Tue, 27 Jul 2010 14:50:46 +0000

Doubling the amount of hardware as the initial amount of hardware increases is indeed exponential. But only because the problem has been set up that way.
I would set it up as the cost of adding capacity for n more users, which is linear in n, at least in this model.

I do see your point however, that software optimization need not necessarily grow more expensive with the amount of hardware backing it. In the real world however, who knows what the growth in costs is? I don’t. Programs often grow in sophistication with the number of users, so the program isn’t stable across this growth. Plus there are a few thresholds after which deployment costs jump.

By: stephan

stephan — Tue, 27 Jul 2010 11:58:16 +0000

@Marc: Constant growth in percent is exponentially in numbers. I think this is clear from the post – perhaps go back and read it again? If it is still not clear I’ll add a paragraph.

By: Marc

Marc — Tue, 27 Jul 2010 11:16:58 +0000

Thanks, that you clarified the relationship between growth of servers and growth of users in your last comment. The servers are only growing exponentially if your users/load are also growing exponentially and not by some mysterious law ;)

Maybe correct this also in your post? I mean, happy company which doubles their userbase regularily, but it’s by no means a law and thats somehow the gist of your second paragraph…

By: stephan

stephan — Tue, 27 Jul 2010 05:06:52 +0000

Or better: If your growth is exponential, your server costs are exponential, while your software optimization costs are constant.

By: stephan

stephan — Tue, 27 Jul 2010 05:00:46 +0000

@Nick: The cost for adding 100% capacity is growing exponentially.

1 server => 1 server
10 servers => 10 servers
100 servers => 100 servers

1,10,100 is not linear.

The correlation between customer growth and hardware growth is constant.

By: Nick

Nick — Mon, 26 Jul 2010 20:32:33 +0000

The examples you give are linear =P. 100 servers cost 100x more than one server.

An example:

Let’s say you have 1000 customers and one server.

If you could just add 1 server and be able to support 2000 customers that’d be awesome (and linear growth). Eexponential growth would be in order to double your customers you needed to add 10 servers.

By: stephan

stephan — Mon, 26 Jul 2010 18:55:30 +0000

Although I’m not the best in mathematics*, I would not call that linear but exponential.

*) as in got my diploma in mathematics but didn’t choose to study mathematics

By: hgabreu

hgabreu — Mon, 26 Jul 2010 18:43:11 +0000

“As this gets expensive very fast (exponentially)- not in…”
The way you explained is seems like a linear growth, not exponential, isn’t it?
100% of 100 = 100 and 100% * 1000 = 1000?