On Mon, May 9, 2016 at 7:18 AM, Ronald Kelley <rkelley...@gmail.com> wrote: > Greetings all, > > I am trying to get some data points on how many containers we can run on a > single host if all the containers run the same applications (eg: Wordpress > w/nginx, php-fpm, mysql). We have a number of LXD 2.0 servers running on > Ubuntu 16.04 - each server has 5G RAM, 20G Swap, and 4 CPUs.
When you use lxd you can already "overprovision" (as in, the sum of "limits.memory" on all running containers can be MUCH greater than total memory you have). See https://insights.ubuntu.com/2015/06/11/how-many-containers-can-you-run-on-your-machine/ for example. I can say that swapping will -- most of the time -- kill performance. Big time. Often to the point that it'd be hard to even ssh into the server to "fix" things. Which is why most of my servers are now swapless. YMMV though. Do some experiments, monitor your swap activity (e.g. use "vmstat" to monitor swap in and swap out), and determine whether swap actually helps you, or cause more harm than good. Also, what's the story with the 5G RAM? Even my NUCs has 32GB RAM nowadays. > I have read about Kernel Samepage Memory (KSM), and it seems to be included > in the Ubuntu 16.40 kernel. So, in theory, we can over provision our > containers by using KSM. > > > Any pointers? I'd actually suggest "try other methods first". For example: - you can easily save some memory from php-fpm by using "pm = ondemand" and a small number in "pm.max_children" (e.g. 2). - use shared mysql instace when possible. If not, use smaller memory settings, e.g. http://www.tocker.ca/2014/03/10/configuring-mysql-to-use-minimal-memory.html This entry from openvz should be relevant if you still want to use KSM for generic applications running inside a container: https://openvz.org/KSM_(kernel_same-page_merging)#Enabling_memory_deduplication_in_applications -- Fajar _______________________________________________ lxc-users mailing list lxc-users@lists.linuxcontainers.org http://lists.linuxcontainers.org/listinfo/lxc-users