On Fri, Jun 15, 2007 at 02:14:43PM -0400, Jon LaBadie wrote:
> On Tue, Jun 12, 2007 at 04:27:32PM -0400, Charlie Reitsma wrote:
> > Has there been any work on amanda being aware of backups going to  
> > virtual tape and then the virtual tape being archived to real tape?  
> > I'd love to be able to keep as much as possible on virtual tape but at  
> > some point I need to archive the data to an offsite location. But in  
> > order to do a restore I would need the index of the virtual tape  
> > associated with the real tape. Very likely, multiple real tapes would  
> > be required to hold a single virtual tape so the index might need to  
> > be rewritten to reflect the media change. I see the move from virtual  
> > tape to real tape more of a tape duplication  - almost as if the  
> > virtual disk were looked at as the holding disk being flushed to tape.

To Charlie's initial question -- this is a *hard* problem, and one for
which a complete answer is a long, long way off.  However, we are
looking in that direction.  In fact, the Device API is a step along the
way, as it gives us a consistent way to talk about different devices
(e.g., vtape and tape) and moving data between them.

> Related to potential projects such as Charlie suggests:
> 
> Does an documentation exist that might be called "Amanda Internals"?
> Things that describe the backup process, authentication procedures,
> network communications and particularly for this project, amanda
> data location, layout, and parsing info?
> 
> Obviously several amanda utilities can access these data.  For example,
> amoverview can lookup the dates and levels for each active DLE backup
> and amrecover can determine on which tapes they are located.  But
> aside from reading the sources for these utilities is the location
> and procedure for accessing these data documented somewhere?

We created the "Developer Documentation" section on wiki.zmanda.com a
few weeks ago.  It's far from comprehensive, but it contains links to
all of the developer-targetted documentation we could find, which
includes descriptions of many of the APIs, authentication methods, and
data storage formats.

The (small) parts of that section that I wrote myself are based on
things I learned while exploring new areas of the codebase.  If someone
wanted to take on a significant project in Amanda, I think it would make
sense to leverage the exploration that would take place to generate some
additional developer documentation.  

Dustin

-- 
        Dustin J. Mitchell
        Storage Software Engineer, Zmanda, Inc.
        http://www.zmanda.com/