[Samba] Is Samba Shadowcopying can be used in Production Environement with more than 20 TB of data

[Adam Tauno Williams]

> > We have something setup here (on a smaller scale) that might be 
> > useful. Our main file server rsync's with our backup server every 
> > hour (using hardlinks to keep snapshots). Since relatively little 
> > data changes between each sync, it is fairly fast (approx 5 minutes 
> > with no noticable slowdown for the clients) the backup server can 
> > then take as long as it likes to write to tape/etc without affecting 
> > the main server. 
> How well does this work on a live filesystem?

Badly.  rsync is a really cool tool for transporting data;  but it
should never be mistaken for a real backup tool.  It isn't one.  Active
files will either be skipped or very likely trashed (on the backup copy)
which isn't a backup at all.

> Are collisions handled gracefully? 

It doesn't.

> For example, what happens when a file 
> is in the process of being rsynced at the exact moment it is in the 
> process of being written to?

You get junk.

A real backup requires the applications (in this case, functionally, the
Windows clients) to be quiescent (including having commited/fsync()'d
pending writes),  rsync offers nothing at all to facilitate that and
isn't even aware of it.

It is probably better to LVM snapshot and rsync from the snapshot,  at
least then you are rsync-ing a single point in time and not a 'rolling'
filesystem.  But even that doesn't promise that files are in a
consistent state.

-- 
          Consonance: an Open Source .NET OpenGroupware client.
 Contact:awilliam at whitemiceconsulting.com   http://freshmeat.net/projects/consonance/