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Microsoft has been taking more and more interest in networked storage and backup in recent years. Windows Storage Server was followed by the likes of Volume Shadow Copy Service (VSS), and now the company has released beta copies of version 2 of Data Protection Manager (DPM), its continuous data protection tool.

So why is an application software and operating system company getting into the backup business? There's two main reasons, argues DPM product manager Bill Shelton - the first was the dramatic shift away from tape over the last year or two, and the second is the realisation that backup is not about data, it's about exactly those applications and operating systems.

"Where we can add more value is in deep integration with Microsoft applications," he says. "Protection is not just backing up the data, it's about recovering the application. It's not disk volumes, it's the data assets that constitute a service."

So DPM, like other continuous data protection (CDP) tools, takes regular copies of application data and saves them onto a dedicated server. Then, if the application data becomes damaged - or if a user deletes data by mistake - it can be recovered from the most recent saved copy. It also has a self-service recovery mechanism that lets the user look after reverting to a previous file version.

Shelton says that Microsoft learnt a lot from DPM v1, not least the need to protect applications in greater depth and more frequently - and without quiescing the application to make it inactive while the backup takes place.

It also realised that, despite disk taking over in many backup roles, organisations still needed tape, either for cheap long-term storage or simply because it makes them feel more comfortable. So where with v1 you could use standard backup software to protect the DPM server, in v2 the DPM server can write extra copies of the data it's protecting straight to tape, and because its version is read-only there are no quiescence issues.

No more backup software?

"Version 1 was a big bid on disk-based backup," he says. "It's becoming disk for recovery, tape for off-site backup and long-term retention. With version 2, third-party backup software is still supported but it's not necessary. It means DPM can now integrate non-disruptively - we have done a lot of work to make it non-disruptive."

That might be bad news for the likes of EMC Legato and Symantec, but Shelton claims it will simplify things for system administrators.

"People are looking at the cost of protecting Exchange, for example, and finding it excessive," he says. "One thing was the inherent limitations of tape, then it was complexity. Backup has become a rat's nest of 50,000 jobs firing off every night, so change management is a very difficult issue.

"We think the best solution is tightly integrated with the application - a simple solution where you define your protection needs and levels, and we then translate that into the jobs needed to implement it. Then, when changes are needed we can see how to adjust those jobs."

He adds, "Version 2 will add a lot for SQL-Server, Exchange and Sharepoint administrators because it already knows what to protect, such as registry keys - Sharepoint is an application that has complexity in recovery, for example.

"We had been public about protecting applications, but not about including tape. We had agents to talk to the backup software, so the data on tape looked like it came from the original server, not the DPM server."

Defence in layers

According to Shelton, Microsoft has also realised just how layered most real-world IT environments are, with different data protection technologies overlapping and working at different levels. He says that it has identified three main data protection layers, which it is now working to address and pull together.

The first is DPM and the recovery console, and the second is operating system tools such as the VSS Writer image-based backup feature in Longhorn. Then there are the protection features within applications, for example local and cluster replication in Exchange 2007, and SQL-Server remote mirroring.

Microsoft's CDP rivals such as EMC and Symantec have attacked DPM for allowing changes to be backed up at most once every 15 minutes, whereas their software really can be continuous, copying changes on the fly. Shelton claims they address a different need though.

"Continuous DPM is a relatively new concept in software," he says. "There is a CDP appliance market out there, but those are such a different market and a different price-point.

"People head for DPM for different reasons," he continues. "The first is it's an application, sold in appliance form, you push out the agent and set your protection policy and you're done. Second, it works very well in distributed environments and reacts well to WANs - it will buffer to take account of outages.

"One of the things that surprised us was the version 1 had a big uptake in distributed environments. It was getting backup out of the edge and back into the data centre. Microsoft has a strong presence at the edge and backup was problematic there.

"DPM also plays a role in WAN acceleration because it is an intelligent replication engine, so it only moves the changes. It doesn't remove the need for WAFS though - it's a different approach."