Les Mikesell wrote at about 15:23:41 -0500 on Monday, August 31, 2009:
 > Jeffrey J. Kosowsky wrote:

 > > More generally, we would need to consider two things:
 > > 1. What are the normal ways in which the two could get out of synch
 > >    and then address each of those cases
 > 
 > Start with that copy you wanted to be able to make.  If the files and 
 > metadata are separate things, there will clearly be times they are out 
 > of sync and lots of opportunity for them to stay that way.
 > 

I don't see the issue here.
- New files are created only when a new file is added to the
  pool. Since this happens coincident with the need for a new database
  entry, these two operations can be synchronized

- Files are deleted or moved (i.e. renamed) only as part of
  BackupPC_Nightly. Since this happens only once a day the database
  can be locked appropriately when this process is running to make
  sure that no files are deleted or renamed without being checked
  against or synchronized with the database

- Potential race conditions might exist if multiple copies of
  BackuPC_dump are running but these would be caught first at the
  database level where collisions can be prevented within the database
  itself assuming that file creation is made to follow database entry.

- Otherwise, I don't see how BackupPC could possibly change files out
  of synch with the database except for external events such as
  crashes, disk errors, or malicious intervention - but all of these
  apply also to the existing BackupPC implementation.

Perhaps other cases exist, but I'm sure once specified, they can be
dealt with too.

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