What you will learn from this tip: Before you
Besides movie-star looks and a winning lotto ticket, what do storage managers want? W. Curtis Preston, vice president of service development at GlassHouse Technologies, thinks better backup is next on the list: "Everybody wants to stop doing fulls for no reason," he says. "It's silly that we're going back out to the clients to get data we already have."
That's the motivation for synthetic full backup, which, with the introduction of Veritas' NetBackup 5.0 last year, is now a core feature of all the major enterprise backup packages in some form or another. Those include CommVault's Galaxy, EMC's Legato NetWorker with Saveset Consolidation and IBM's Tivoli Storage Manager (TSM) with the notion of Backup Sets.
And now Sepaton, a startup that sells the S2100 virtual tape library (VTL) appliance, has announced a new approach to synthetic fulls that borrows from the idea of a point-in-time snapshot. Thanks to its "content-aware architecture," which understands the Veritas NetBackup data format, Sepaton can scan an incremental backup stored on the S2100 and create a new full simply by supplying a pointer to that data.
It's easy to see the attraction of synthetic fulls. In a nutshell, they cut down on the time you spend doing full backups, freeing the application servers and network, and they make for faster restores. "With a synthetic full, you essentially do half of the restore operation in advance," says Veritas' Adams. That means that come restore time, a system can be recovered from a single backup tape or backup set.
But there are downsides to synthetic fulls, says Tricia Jiang, technical attache for IBM's TSM. While you no longer have to do full backups of your client machines, synthetic fulls require substantial amounts of time and hardware on the media server side.
"They take a fair amount of resources," such as tape hardware and media servers that may otherwise be occupied doing restores or tape clones, says George Symons, EMC's chief technology officer of information management. "You definitely have to plan for it."
GlassHouse's Preston concurs with that assessment. Indeed, "in some cases, it may actually take more time to do a synthetic full than to do a regular full backup," he says. "You kind of need to really want it," where "it" is a shortened backup window, reduced network traffic and faster restores.
For more information:
Advice: How fast will my backups run?
Tip: Don't fight your DBA
About the author: Alex Barrett is "Storage" magazine's trends editor.
This was first published in November 2004