HDF5 is pretty terrible as a wire format, so it's not a 1-1 comparison to Arrow. Generally people are not going to be saving Arrow data to disk either (though you can with the IPC format), but serializing to a more compact representation like Parquet.
As I understand, arrow is particularly interesting since itβs wire format can be immediately queried/operated on without deserialization. Would saving an Arrow-structure as parquet not defeat that purpose, since your would need the costly deserialization step again on read? Honest question
The FAQ [1] and this SO answer [2] explain it better than I can, but basically yes. However, the (de)serialization overhead is probably better than most alternative formats you could save to.
