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Shared CPU, noisy neighbours, and what you are actually renting
How shared hosting divides a machine, what a noisy neighbour really does to you, and when a dedicated core stops being a luxury.
Эта статья пока на английском. Мы её переводим.
Almost all hosting is shared: one physical machine, several tenants, an allocation each. That is not a problem in itself. It becomes one when the allocation is a share of whatever is left rather than a reservation, because then your performance is a function of somebody else's evening.
What a noisy neighbour looks like from inside
Your own graphs look fine. Memory is calm, your process is not doing anything unusual, and yet the tick rate wobbles at times you cannot explain. That pattern - unexplained variance with clean internal metrics - is the signature.
- Consistent slowness is usually you.
- Variable slowness with quiet internal metrics is usually the machine.
- Slowness at the same time every day is usually a scheduled job, yours or somebody else's.
When dedicated is worth it
For most servers, never. For a competitive game where tick consistency is the product, or an application with a latency budget you have promised somebody, a reserved core is the difference between a good average and a good worst case - and the worst case is what people remember.