It seems the xarray object that is sent to the workers contains a reference to the complete graph:

```python vals = da.random.random((5, 1), chunks=(1, 1)) ds = xr.Dataset({'vals': (['a', 'b'], vals)}) write = ds.to_netcdf('file2.nc', compute=False)

key = [val for val in write.dask.keys() if isinstance(val, str) and val.startswith('NetCDF')][0] wrapper = write.dask[key] len(pickle.dumps(wrapper))

14652

delayed_store = wrapper.datastore.delayed_store len(pickle.dumps(delayed_store))

14652

dask.visualize(delayed_store) ```

The size jumps to the 1.3MB if I use 500 chunks again.

The warning about the large object in the graph disappears if we delete that reference before we execute the graph: key = [val for val in write.dask.keys() if isinstance(val,str) and val.startswith('NetCDF')][0] wrapper = write.dask[key] del wrapper.datastore.delayed_store It doesn't to change the runtime though.