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KVM virtualization: How much isolation / resource guarantee does it provide?
We are assuming no malicious intent users in this scenario.
If an end user is using a KVM VPS, and they max out all available resources CPU/Disk/RAM/Network.. which resources will impact other clients? If a provider wants to allow end user to do what they want in their VPS, does KVM provide technology to allocate such limits, such that other VPS are not impacted by actions of one VPS? Does KVM allow resource guarantees?
Comments
Fairshare CPU = inpact for everyone, when the HDD is used hardcore it breaks all other VM's down. Network its basically the same you get high latency but RAM would be one point when you dont mount it as RAM Disk and abuse it like the HDD it should not slow anything down. Correct me when i am wrong.
You can provide resource guarantees by pinning the VM to a specific subset of CPU cores. For disk, you can use raw disk format without sparse file so that is guaranteed as well. Network and RAM are harder to do, although you can of course solve RAM by not overallocating RAM (the hypervisor exposes a specific memory pool to each VM, so this isn't hard to do; OpenVZ for example maybe a bit more confusing since it's more direct with host), and there are ways to rate limit network usage.
If you are not able to control the hypervisor (i.e. you are buying from another provider) then of course there are no guarantees for any resource, other than service-level guarantees...
@perennate , Agreed. +1 for that point of view.