[ceph-users] libRADOS semantics

are there any good documents on the implicit requirements for librados calls? I can write a file, if it doesn't exist successfully. I can write_full a file, and it works (but many of my files will need to be chunked off disk, not enough RAM) I can append to a nonexistent file and it works. I *cannot* write to a part of an existing file (overwrite a section of it or write past it's current size) --> Errno 95 I *cannot* append to an existing file --> Errno 95 I *cannot* trunc an existing file (nor a non existent file) --> Errno 95 (what is the point of this then??) any ideas / where can one see more detailed semantics of what operations are allowed and when? The librados C API does not really go into any detail about errors and why things happen as they do. This behavior seems similar whether I am admin or a separate user. Thanks for any pointers. Cary