[clug] peformace of Containers vs virtual machines

[Sam Parkinson]

Hi George,

I've done some Docker sysadmin stuff for various orgs over the last few
years.  Hope some of this helps:

Docker is a container system that is geared towards containers that run
1 app.  For example, you would have a container that only ran your
minecraft server, or a container that nginx, etc.  It has a lot of
tools that make it quick and easy to build containers; you just write a
`Dockerfile` that specifies commands to run to setup the
container.  Docker is an app that is quite focused on sysadmin
experience.

I'm not an expert in LXC, but I think it is more geared towards
containers as being just VMs with a different technology.

IIRC Docker does not limit the resources of the container by
default.  Containers are just processes running on your kernel; a
modern version of a chroot.  You can go an add limits; but possibly
more easy to change and configure than with libvirt.  This might mean
you get better performance for your game server, as it can use the
entire CPU.  (Or you can limit it if you don't want better perf)

Since docker containers run within the same kernel, there is less
overhead (as they are not a VM).  Obviously the extent of the overhead
removed depends on your configuration and CPU model.  I can't find
great benchmarks on the net, but results vary a lot [1][2].

One pitfall is docker does funky stuff in the network stack.  This will
introduce extra latency; which could impact your game server.

[1] https://www.slideshare.net/Flux7Labs/performance-of-docker-vs-vms/1
8
[2] https://stackoverflow.com/a/26149994

On Sat, 2018-02-03 at 19:52 +1100, George at Clug via linux wrote:
> Bob and other Container experienced people,
> 
> My family loves playing Minecraft, particularly Feed The Beast (FTB)
> mod packs like Infinity and Direwolf 20.
> https://www.feed-the-beast.com/
> https://www.feed-the-beast.com/projects/ftb-presents-direwolf20-1-12
> 
> At home we use a Debian KVM lib-virt server (32 GB RAM, i7) to run the
> FTB server, while using Windows for the client computers.
> 
> On the windows clients these mods can use up to 12 GB of RAM and do
> not like running in environments with less than 8 GB.
> 
> The FTB server only consumes about 3GB but it tends to max out the
> virtual CPU resources. This causes lag in the game, and the
> FTB/minecraft server complains about not being able to keep up.  I
> have tried adding more cores, and/or CPUs but this has not helped. 
> Maybe there is a way in virt-manager where I can allocate more CPU
> resources by using other means?
> 
> The Debian server exists for our family to play networked games,
> naturally we tend to play only one game at a time, sometimes this will
> be a vanilla minecraft, other times FTB, other times Ark Survival
> Evolved, etc. 
> 
> Bob,
> 
> Do you think I would get better performance from using Containers? 
> 
> As I am using Debian, which container system should I install ?  
> 
> Doing a search on the internet there seems to be Linux Containers
> (LCX) and Docker.  Are these things the same? or are they alternative
> container systems?  Is one the management system for the other?  (I
> should not be so lazy in asking and just do some reading)
> https://wiki.debian.org/Docker
> Docker [1] is a solution for the management of lightweight process
> containers. 
> https://wiki.debian.org/LXC
> Linux Containers (LXC) provide a Free Software virtualization system
> for computers running GNU/Linux.
> 
> I have never bothered using Containers previously. I have enjoyed
> using Virtual Machines and previously these have been adequate. Sadly
> heavily modded minecraft servers tend to consume lots of CPU
> resources.
> 
> Comments, please...
> 
> George.
> 
> 
> 
> 
> 
> 
> 
> Links:
> ------
> [1] http://docker.io/