Disk size is parsed using `units.RAMInBytes`

I was surprised that `100MB` is parsed as `100MiB`, as I expected the field to accept the same kind of units as Kubernetes resources (https://github.com/kubernetes/apimachinery/blob/master/pkg/api/resource/quantity.go).

Not sure if the Kubernetes package is re-usable from outside Kubernetes. If it isn't, then I think it would make more sense to parse disk sizes using `units.FromHumanSize` because disk sizes are customarily specified in decimal SI units.