In my opinion configuration resolution will be best if resolved in the following order of increasing priority/weightage.

1. Auto-detect depending on the system parameters.

Auto-detection of best params is a must IMO as there's

enough diversity in server hardware that one size won't fit

all can be implemented without much effort(excluding benchmarking).

2. Configuration file: A yaml, toml, or any other simple format

- Load a different config file with *nbdcopy --file=custom-config.yaml*

- Maybe generate the default config file having values from the auto-detect phase.

nbdcopy --generate-config

3. CLI params

A quick way to override configuration file params

ex: functionally same

`nbdcopy --requests=4 --config=custom-config.yaml`

`nbdcopy --config=custom-config.yaml --requests=4`

The flow of initialization:

Read config file ----override ---> CLI params --- missing params --> auto-detect fill

or

easier implementation:

auto-detect fill --- override ---> config file --- override ---> CLI params

The rationale for choosing configuration file method:

- Easier to use avoiding long commands (less typing, scripts easier to read)

- Easy switch between multiple configurations and override them.

- Documentation and configuration in the same place

So easier for someone else to understand why certain parameters were chosen.