is it possible to speed up writes inside a docker container?

Question

I have a very large file in my docker container (it's a virtualbox image) which --- unfortunately -- must be modified as part of running it. Docker's copy-on-write policy works against me here and unfortunately any mutation/copying of the file takes about 10 minutes, compared to about 10 seconds to copy the same file on the host.

Can anything be done to speed up the creation/copy of very large files within a docker container? Note that this is an entirely transient file that I do not need to persist after the container is closed.

Answer 1

Declare the folder the file is in as a volume. If you do this, the copy-on-write-policy is not applied. Note that you don't have to mount this volume to the host system, it is sufficient to declare it as a volume.

For more information: https://docs.docker.com/userguide/dockervolumes/