* SIGWINCH/SIGHUP to stop/restart worker threads during upgrade
* hot management interface
* reduce/minimize memory/stack usage
  - switch from gnulib/hash to khash
* optional fsync/fdatasync/O_SYNC/msync for PUT (how?)
* fallocate support?  slow emulation interfaces can be a problem...
* inotify (and kqueue) support for detecting new device directories
* cleanups: favor ccan/{list,container_of,check_types} ...
* rewrite test suite using Perl5 (Ruby language is too unstable)