News and updates from DockerCon 2015

Posted Jul 2, 2015 16:43 UTC (Thu) by rriggs (guest, #11598)
In reply to: News and updates from DockerCon 2015 by raven667
Parent article: News and updates from DockerCon 2015

> It was never anyones goal to virtualize the machine such that you needed to run nested kernels

Huh? How would one run a Windows OS on an Apple laptop without nested kernels? It is certainly a reasonable goal to do that. And with VMWare, there is no nesting of kernels -- just a hypervisor and non-nested OS peers. With Docker, it seems that one gives up OS flexibility for a little hardware efficiency.

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News and updates from DockerCon 2015

Posted Jul 2, 2015 16:47 UTC (Thu) by jberkus (guest, #55561) [Link] (1 responses)

It's more than a *little* hardware efficiency. As an example, I can easily run four to six containers on my ultralight laptop and still do a presentation with LibreOffice slides. Whereas, if I run *one* VirtualBox VM, that's pretty much all I can run. In production, this means running 4 to 40 containers per machine, instead of 1 to 4 VMs.

So to rephrase: "giving up some flexibility for order-of-magnitude better hardware efficiency," which seems like a reasonable tradeoff. Sometimes you need a full VM, but often you don't.

News and updates from DockerCon 2015

Posted Jul 7, 2015 4:17 UTC (Tue) by Gnep (guest, #102586) [Link]

Not necessary, check out www.hyper.sh. You can certainly run hundreds or even thousands of these ultra light VMs per server.

The flexibility tradeoff is not made by Docker. It is instead container VS hypervisor. For a public CaaS platform, BYOK (bring-your-own-kernel) is necessary. Read more: https://hyper.sh/blog/post/2015/06/29/docker-hyper-and-th...

News and updates from DockerCon 2015

Posted Jul 3, 2015 2:14 UTC (Fri) by raven667 (subscriber, #5198) [Link]

> How would one run a Windows OS on an Apple laptop without nested kernels?

I'm not sure how that's relevant to a discussion about Docker which largely about servers, especially servers running Linux where it solves a software deployment problem with lower overhead than full machine virtualization solves the same problem.

> And with VMWare, there is no nesting of kernels -- just a hypervisor and non-nested OS peers.

I don't think that's how it works, the vmkernel hypervisor kernel is the primary kernel, all of the other OS kernels are subordinate to it and nested inside the interface which is controlled and provided by the vmkernel. This is highly performant in that the interface is often provided directly by hardware which has the capability to segment itself, such as an IOMMU or VT instructions and a new layer of page tables, with that segmentation controlled by the vmkernel. The vmkernel is the only kernel with a full and complete view of the hardware, the OS kernels which run under it are the only ones privy to the userspace processes and syscall API state.

> With Docker, it seems that one gives up OS flexibility for a little hardware efficiency.

Docker is only targeting Linux, and allows you to migrate from a bunch of Linux VMs on Xen, KVM, or VMware (I guess HyperV too), to running the same software on bare metal using namespaces, changing one management framework for another and removing a layer of abstraction which gets a performance benefit.