On Wed, Jan 16, 2008 at 08:44:09AM +0930, Alan Rubin wrote:
> Hello,
> 
> We have encountered a NetWorker behavior wherein the saveset being
> backed up on the NetWorker server is significantly larger than the
> source data.  In some cases the saveset is larger than the physical
> disk from which the data is being retrieved.

This is easy to do if the file is "sparse".  I can create a file that
has only a few valid blocks in it, but they are located at a high
offset (such that the "length" of the file is many gigabytes).  

I believe that Networker's "save" will not do special processing of it
as sparse, but will back up all the implicit zeros at the beginning.

> I believe this problem may be caused by client files being
> touched/open/updated during the backup period; however, NetWorker's
> reaction to this activity is far from ideal.  It's a waste of network,
> disk and tape resources which we can ill afford.  Does anyone know how
> NetWorker should behave when it tries to backup a file/saveset that
> changes during the backup?  Is there any way to change this behavior?

I've not seen anything similar.  I believe all it does is "read" the
file from front to back.  If the file changes during that period, it
logs a warning.  I've never seen it go back and attempt to pick up the
changes by reading it multiple times.

> We are running 7.3.3 Build 510 on a Sun T2000 running Solaris 10 08/07.  The
> clients where we have definitely seen this affect are Windows servers.  Our
> clients mostly still run a 7.3.2 version of the client.

I have no idea if "sparse" files exist on NTFS filesystems.  Are you
using any type of open file manager?  I would expect that otherwise the
backup of the file would simply fail.

-- 
Darren Dunham                                           ddunham AT taos DOT com
Senior Technical Consultant         TAOS            http://www.taos.com/
Got some Dr Pepper?                           San Francisco, CA bay area
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