May be this is not a question but feature request. 1) I want to know how partially download file. Specifying bytes range would more than ok. 2) I want to know how partially upload file. In general append feature would be extremely desirable. Specifying bytes range would more than ok as well. Metadata api excellent in current state, but file modification api is really lacks these two features. Could you please help me to identify supporting API or add it to feature request list? PS: May be some delta-based API would be great too.