issue_comments: 1450727551

I do generally recommend cache_type="first" for reading HDF5 files, because they tend to have most of the metadata in the header area of the file, with short pieces of metadata "elsewhere"; so the default readahead doesn't perform very well.

As to what the two writers might be doing differently, I only have guesses. I imagine xarray leaves it entirely to HDF to make whatever choices it likes. Dask does not write in parallel, since HDF does not support that, but it may order the writes more logically. It does set up the whole set of variables as a initialisation stage before writing any data - I don't know if xarray does this.