On Sat, Jun 06, 2009 at 03:20:44PM -0400, Jorge F?bregas wrote:
> I'm still learning Netbackup (got around 1.5 years working with it) and I'm 
> wondering... Is there a way to perform incremental backups using in-file 
> delta technology (backup only changes within a file)?  I've seen a lot of 
> features/options for Netbackup but I have never seen this...If indeed there 
> isn't ...why isn't this type of ESSENTIAL technology part of
> Netbackup?

Are there any common backup solutions that do offer that feature?

Untless the filesystem is giving hints to backup program (and I don't
know any that do), you'd have to compare the old file to the new file to
understand which blocks have changed.  The base product can't do that.
The only information it has about backup needs is the timestamp (or on
Windows, the archive bit).

Assuming the previous file is on tape, comparing against it would
require reading that tape first.  If that's a different tape, you now
need two tape drives.  If it's the same tape, you can't read and write
to it simultaneously.  More slowness.

Keeping track of blocks is standard for a de-duplication solution.
That would be designed with proper indexing structure and sufficient
disk space to find and validate data without causing a huge slowdown
during backups.  There's lots of standalone products, or you could look
at the Symantec PureDisk solution.

> Just as an aside, I recently started backing up a server that runs "MS 
> Virtual 
> Server" that has around 9 guests...I back them up at night (obviously after 
> shutting down the guests) and I know 5 of those 9 guests seldomly change but 
> as you can imagine...because the timestamp on the virtual-hard-disks 
> change ...they're backed up COMPLETELY.  The end result: I'm almost 
> performing a FULL backup every day even though it's an incremental 
> schedule   :(  

Yes same with doing file-level backups of a database.  Similar options
apply:  

* Run some sort of de-dup product
* Backup from within the virtual host, not the image files from the
  server
* Live with the size hit and delete things quickly

-- 
Darren
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