[wwarner]

Great intel from on the ground. The story arc makes total sense. I also have starry eyes for orchestrated unikernels, but otoh linux is so configurable scaling down the kernel also seems very reasonable. How do the boot times compare? To me, the unikernel's chief appeal is that it could potentially start up in about the same amount of time it takes to load a native binary. Thanks for sharing.

[justnoise]

On bare-metal boot times are drastically different. OSv was sub-second while our Alpine images were 3-5 seconds depending on what services we needed. However, we were focused on running our system on cloud VMs, not bare-metal. In the cloud you can't get a VM to start booting in less than 20-30s so that order of magnitude difference turned into, at most a 10% difference in boot times.

In 2017 we measured the restart time in of our unikernel images in AWS to be 22 seconds, all that time was waiting for Zen (2017... no KVM yet) to get around to getting to the place where we could run our image. So for our use case, the boot time didn't actually matter, it was far overshadowed by everything else happening under the hood.

I should say: Unikernels do have their advantages and should be used in areas that can exploit those advantages: Fast boot, low attack surface, way better performance for some workloads. We had trouble finding the specialized customers in the cloud that needed any of a unikernel's positives so badly that they would take on a unikernel's shortcomings.