In order to provide a high performance backup and restore solution that scales to very large capacity devices and networks, the storage daemon must be able to extract as much performance from the storage device and network with which it interacts. In order to accomplish this, storage daemons will eventually have to sacrifice simplicity and painless portability in favor of techniques which improve performance. My goal in designing the storage daemon protocol and developing the initial prototype storage daemon is to provide for these additions in the future, while implementing an initial storage daemon which is very simple and portable to almost any POSIX-like environment. This original storage daemon (and its evolved descendants) can serve as a portable solution for non-demanding backup requirements (such as single servers of modest size, individual machines, or small local networks), while serving as the starting point for development of higher performance configurable derivatives which use techniques such as POSIX threads, shared memory, asynchronous I/O, buffering to high-speed intermediate media, and support for tape changers and jukeboxes.
Kern Sibbald 2010-08-30