> 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?

As others have said this is what all deduplication products do, at least 
for any file larger than their minimum.  Most have a window size of a 
certain number of blocks that they look at, calculate a hash value, and 
then see if they already have that hash stored in their tracking database 
- if they do then they just replace the data with a pointer to the blocks 
already stored.  There's a lot more detail, and it is the detail that 
differentiates the various solutions out in the market.  Files below a 
certain size are just backed up anyhow as it takes longer to do the sums 
than it is worth.

To say NetBackup doesn't do this isn't quite accurate.  It supports lots 
of different VTLs and now several OpenStorage products that include 
deduplication, so at the point where the backup is stored you can get your 
savings - for example your virtual machine backups I'm sure would 
deduplicate very well.  What that doesn't save you is actually reading the 
backup off the disks and sending it all the way to the backup storage 
device.

If you use NetBackup PureDisk Deduplication Option (PDDO), the 
deduplication happens at the NetBackup Media Server.  That Media Server 
could be 'close' to the clients - in Solaris it could be the global zone 
of a zoned server.   I'm not sure if the Media Server is yet supported in 
a VM; the Master is now, and I can't see any technical reason why for a 
network-attached storage unit like PDDO it couldn't be supported from a VM 
(asides from needing to resource the VM enough) - so you might be able to 
have the Media Server in the same physical server as the backed-up VMs.

If you use Symantec PureDisk the deduplication happens in the client (i.e. 
your VM) but PureDisk is not NetBackup.  EMC Avamar is also in-client 
deduplication.

William D L Brown



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