[apphrase]

Can anyone please tell about the overhead of Docker, compared to no-container scenario (not against a fat vm scenario)? I am a "dev" not "ops", but we might make use of Docker in our rapidly growing service oriented backend... Thanks

[shykes]

For process isolation, the overhead is approximately zero. It adds a few milliseconds to initial execution time, then CPU and memory consumption of your process should be undistinguishable from a no-container scenario.

For disk IO, as long as you use data volumes [1] for performance-critical directories (typically the database files), then overhead is also zero. For other directories, you incur the overhead of the underlying copy-on-write driver. That overhead varies from negligible (aufs) to very small (devicemapper). Either way that overhead ends up not mattering in production because those files are typically read/written very unfrequently (otherwise they would be in volumes).

[1] http://docs.docker.io/en/master/use/working_with_volumes/

[apphrase]

VEry good answer, thank you. So in my scenario, I was thinking of packaging our service apps (which run on JVM) and if I make sure that the OS has jvm and all the needed stuff ready. Shipping a package and deploying the service, is just transferring the Docker container and run it. Which happens to be using the same process models as the OS itself. So in other terms, Docker is a convenience layer (a glorified FS abstraction). I am not saying this to undermine the utility, just trying to figure out if it solves more problems then the complexity it brings (which is one more moving part in your toolchain)