user3667125's questions

I am running KVM with some Ubuntu VM's as guest machines. The guest machines contain an application that does not need to be run most of the time, but once every few months, there are unexpected, random triggers that require it to be run immediately (<5 second delay) for just a few hours.

If I keep the VM always running, I waste a lot of CPU resources, because the VM is mostly inactive 99.99% of the year.

If I hibernate the VM state into disk, starting the application would require booting the VM up, which takes too long on my machine (minutes).

I'd like to pause/suspend the VMs into memory, because resuming the VM seems instantaneous. And while the VM is inactive, I can re-use the CPU resources elsewhere (although I understand that I cannot re-use the memory).

Is it recommended to pause guest VMs for long periods of times (months or years)? Will it be reliable to resume? What are best practices to make sure it will resume normally when I need it months later?

I was thinking of buying ECC ram for the host machine to protect against random bit flips. But is there anything else I should be doing?

In AWS for example, when I spin up a new EC2 instance, it loads up a new VM, then populate the VM with a container image. This is the reason why spinning up new EC2 instances take 60-90 seconds to start.

Out of curiosity, what are the disadvantages to having AWS run the host machine as-is, and when a user wants to "spin up an EC2 instance", AWS just spins up a container with restricted permissions, and allows the user only access to that container?

The upside would be that the compute instance would spin up very quickly. I'm still learning about cloud technologies, so I was just wondering what the downsides are.

Perhaps it is harder to allocate CPU resources without using VMs? And as a result, users would fight over each other to take the available CPU? Or perhaps there's some security concern? Would love to learn about this.