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Title is kinda clickbaity (wha-? how can a VM be lighter than a container). It's about unikernels.

JeanSebTr 4y ago
Exactly, unikernels are great for performance and isolation, but that can't be compared to a full application stack running in a container or VM.
- OrvalWintermute 4y ago
  Not all containers are a "full application stack" A unikernel can definitely be compared.
nailer 4y ago
Firecracker VMs are considered lighter than a container and are pretty old at this point.
- sidkshatriya 4y ago
  I would say that firecracker VMs are not more lightweight than Linux containers. Linux containers are essentially the separation of Linux processes via various namespaces e.g. mount, cgroup, process, network etc. Because this separation is done by Linux internally there are not that many overheads. VMs provide a different kind of separation one that is arguably more secure because it is backed up hardware -- each VM thinks it has the whole hardware to itself. When you switch between the VM and the host there is quite a heavyweight context switch (VMEXIT/VMENTER in Intel parlance). It can take a long time compared to just the usual context switch from one Linux container (process) to another host (process) or another Linux container (process). But coming back to your point, no firecracker VMs are not lighter/lightweight than a Linux container. They are quite heavyweight actually. But the firecracker VMM is probably the most nimble of all VMMs.
throwaway894345 4y ago
> how can a VM be lighter than a container It's still clickbaity, but the title implies a comparison between a very lightweight VM and a heavy-weight container (presumably a container based on a full Linux distro). You could imagine an analogous article about a tiny house titled "my house is smaller than your apartment".
- marcosdumay 4y ago
  It is still lighter in memory only. CPU is also a relevant thing to compare them.
- turkishmonky 4y ago
  Not to mention, in the paper, the lightvm only had an advantage on boot times. Menory usage was marginally worse than docker, even with the unikernel, and debian on lightvm was drastically worse for cpu usage than docker (the unikernel cpu usage was neck and neck with the debian docker contaner). I could see it being an improvement over other VM control planes, but docker still wins in performance for any equivalant comparisons.
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pjmlp 4y ago
Which in case someone has failed to notice, is pretty much how serverless happens to work out from development point of view. No one cares how the language runtime is actually running.

Exactly, unikernels are great for performance and isolation, but that can't be compared to a full application stack running in a container or VM.

OrvalWintermute 4y ago
Not all containers are a "full application stack" A unikernel can definitely be compared.

nailer 4y ago

Firecracker VMs are considered lighter than a container and are pretty old at this point.

sidkshatriya 4y ago
I would say that firecracker VMs are not more lightweight than Linux containers. Linux containers are essentially the separation of Linux processes via various namespaces e.g. mount, cgroup, process, network etc. Because this separation is done by Linux internally there are not that many overheads. VMs provide a different kind of separation one that is arguably more secure because it is backed up hardware -- each VM thinks it has the whole hardware to itself. When you switch between the VM and the host there is quite a heavyweight context switch (VMEXIT/VMENTER in Intel parlance). It can take a long time compared to just the usual context switch from one Linux container (process) to another host (process) or another Linux container (process). But coming back to your point, no firecracker VMs are not lighter/lightweight than a Linux container. They are quite heavyweight actually. But the firecracker VMM is probably the most nimble of all VMMs.

throwaway894345 4y ago

> how can a VM be lighter than a container It's still clickbaity, but the title implies a comparison between a very lightweight VM and a heavy-weight container (presumably a container based on a full Linux distro). You could imagine an analogous article about a tiny house titled "my house is smaller than your apartment".

marcosdumay 4y ago
It is still lighter in memory only. CPU is also a relevant thing to compare them.
turkishmonky 4y ago
Not to mention, in the paper, the lightvm only had an advantage on boot times. Menory usage was marginally worse than docker, even with the unikernel, and debian on lightvm was drastically worse for cpu usage than docker (the unikernel cpu usage was neck and neck with the debian docker contaner). I could see it being an improvement over other VM control planes, but docker still wins in performance for any equivalant comparisons.

deleted 4y ago

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pjmlp 4y ago

Which in case someone has failed to notice, is pretty much how serverless happens to work out from development point of view. No one cares how the language runtime is actually running.