[femto113]

Cloud providers aren't guessing at demand to plan capacity, they're literally building new data centers and then wheeling new racks into them as fast as they physically can (short-term decisions are more likely made at the other end, e.g. when to retire old systems, not add new ones). AWS was born out of the fact that Amazon's own compute needs are inherently variable so to meet peak demand they had to "over-provision" compared to average demand--this in turn meant they had a lot of excess compute power most of the time. At the point when Amazon still was a dominant consumer of AWS, spot instances were actually a deliberate convenience to Amazon, since it meant AWS could monetize resources while still ensuring Amazon could claim them instantly when needed (later they added a two minute warning, but early on they could literally disappear at any moment, and regularly did).

[Twirrim]

You're talking to someone who has spent the last decade working for major cloud providers, including AWS, on infrastructure and services sides of things, including work around data feeds for the capacity management teams. I have more than a passing familiarity with the way things actually work at a cloud.

They are constantly guessing at cloud capacity. Short, medium, and long term models with forecasting galore, all under constant recalculation based on customer actions (they literally take live feeds of creation/termination actions), and yes they also take in to account hardware failure and repair rates. Consolidating racks of equipment is a pain in the neck and tends to be avoided, unless you can safely live migrate away all instances.

They all build up various models, using all sorts of forecasting techniques. The longer range forecasts are involved in data center provisioning, along with other business analysis, market research, legal analysis etc. that helps define where future regions should be.

It's still a guess. They can't tell what the actual demand will be, and they can't tell what is going to happen with the supply chain (supply chain issues are the biggest nightmare for capacity planning teams). Sometimes they get it wrong.

The capacity management teams spend a lot of time and expertise to keep the company just sufficiently ahead of demand. It's a crucial part of keeping costs under control.

[gerdesj]

It's logistics no more and no less. Logistics has been a thing for ever (satisfy a resource requirement). My old man (is not a dustman) but he was Commander Supply for quite a lot of people. At one job, he and his staff would worry about things like Austrian plain chocolate covered mint centred frogs (I'm not joking) to Gurkha rice and not much else (some very concentrated protein etc) water-proofed combat rations. This was in Cyprus in the '80s. Logistics on the green line in Cyprus is probably still as mad now due to the number of countries in the UN.

Anyway, capacity planning is very well understood in general but of course the devil is in the details.

At the moment the IT supply chain is pretty spotty and that affects my little IT firm up to the big boys.

When you buy Cisco + HPE + Dell or whatevs, you go to your reseller (me). I go to my distributor and they suck hardware out of Dell etc and take their cut and I install the gear and take my cut. Sometimes a disty thinks they can do reseller too. The thinking is that they can roll up two lots of margin and shave a bit. That's fine if you can actually do logistics and the "teeth arm" job too.

Clouds think they can go even further and sometimes they can and sometimes not. Now we have a sodding complicated resource on offer with a supply chain that is a bit random.

The whole hyperscale cloud premise is based on infinite availability of raw resources and that is complete bollocks. You can't hyperscale if you can't source stuff indefinitely.

Those Austrian mint filled choccy frogs became a thing for a while. I gave no idea of the exact numbers but presumably Austria supplied quite a lot of them for the UN forces and families in Cyprus in the '80s - they became a bargaining chip for a while. They came in a cardboard package with a lid coloured light blue with outlines of frogs and I think the main box was dark brown or black.