[sciurus]

I don't see how Docker solves the speed problem without a workflow change that could already be accomplished with Vagrant.

* Install your stack from scratch in 6 VMs: slow * Install your stack from scratch via 6 Dockerfilea: slow * Download prebuild vagrant boxes with your stack installed: faster * Download prebuilt docker images with your stack installed: fastest

The main drawback of Vagrant is that afaik it has to download the entire box each time instead of fetching just the delta. That may not matter much on a fast network.

[nl]

Running 6 VMs has non-trivial overhead though. That just isn't there using containers.

[sciurus]

I have to disagree, although I'll admit that what's "trivial" is subjective. Sure, a container means you don't have to run another kernel. If the container is single-purpose like docker encourages, you skip running some other software like ssh and syslog as well. That software doesn't use much CPU or memory though. I just booted Ubuntu 12.04 and it's using 53MB of memory. Multiplied across 6 VMs that's 318MB, not quite 4% of the 8GB my laptop has. I'd call that trivial.

On the last project where I had to regularly run many VMs on my laptop, the software being tested used more than 1GB. Calling it 1GB total per VM and sticking with the 53MB overhead, switching to containers would have reduced memory usage by 5%. Again, to my mind that's trivial.