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We can expand horizontally (horizontal scaling) or vertically (vertical scaling)
Horizontal scaling
Vertical scaling
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Replicating resources
to
or
The number of instances is limitless
Vertical scaling
Adding more resources to a unit
to e.g. increasing the number of CPUs or RAM
But there is a limit to how much can be added
The OS may not be able to physically access the amount of RAM on the new configuration
The fixed capacity problem
The traditional approach to provisioning infrastructure is to use historical data to estimate the number of required components. The problem is that you would either over-estimate or under-estimate the number of components. Leading to panic buying and provisioning of additional units or having wasted capacity.
An example of the above could be the launch of a web application requiring a number of physical web servers, let’s say 5.
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As with most launches the number of required physical servers will be less then expected.
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But as time progresses and the if the product is successful the initial capacity can be reached very quickly.
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You now have to redo the maths and determine what the new capacity should, so you estimate it to be 10 and provision 10 more servers. But there is a downturn in the market and you now have more capacity than you needed
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And this cycle of wakamo continues
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If you take the traditional approach to provisioning infrastructure,