- to what degree are they modifiable?

I mean:

 - a backup volume - if it can be turned to a read-write one?
   (desirable while reading backups as a disaster recovery,
    last time it was mentioned on the list the answer was "no but may be
    later yes")

 - is it possible to move a volume to another storage group?
   (rearranging servers, moving data between servers)

 - is it possible to change the member list in a storage group?
   modify, add, delete?
   (the same - moving data between servers)

Thanks!
--
Ivan
in the process of rearranging servers :)