Les Mikesell wrote at about 14:36:24 -0500 on Tuesday, June 2, 2009:
 > Jeffrey J. Kosowsky wrote:
 > >
 > >  > 
 > >  > There's only a small difference in scale here (and it's not obvious 
 > >  > which direction) between rsync'ing a raw database file and rsync'ing an 
 > >  > image copy of a filesystem.  There's probably not much of a practical 
 > >  > difference.
 > > 
 > > Except that I have a lot of other stuff on my filesystem so I don't
 > > want to image the whole filesystem.
 > 
 > That just takes some sensible planning...

Needs change, systems grow, systems added. Not all of us can afford to
start with a lifetime of disk space... Not all of us have perfect
foresight when we set up the system the first time...

Suppose I want to change filesystems (say move to ZFS), exactly how do
I do that now other than to do a file copy operation including hard
links that could take the better part of a day or more, assuming it
doesn't crash or slow to a crawl due to memory constraints.

 > 
 > > I just want to image the
 > > backups. Also, not all filesystems support efficient methods for
 > > imaging a partially filled filesystem.
 > 
 > Why is it that you are concerned about efficiency here, but not in your 
 > mythical database system?

I'm not talking about marginal efficiency. I'm talking about there not
being a *practical* way to replicate a large Backuppc pool  in any
reasonable amount of time given the number of hard links other than
imaging the entire filesystem.

 > 
 > > Again, you are assuming a tight
 > > integration between the functionality and setup of the filesystem and
 > > the backup software whereas I want to abstract away any such
 > > requirements as much as possible even at the expense of some extra
 > > overhead.
 > 
 > Somehow I don't see how having to install, tune, and maintain an 
 > otherwise unneeded database fits into the concept of abstracting away 
 > functionality.  You have to live with filesystems anyway so you might as 
 > well learn how to manage them.

I don't see the any major requirement for tuning and maintaining a
metadata database unless you are doing huge enterprise size backups.

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