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Backup for remote and mobile devices

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Another challenge is that the computers being backed up can't be counted on to be powered on at all times the way servers are in a data center. Most laptop users (and users of other types of remote devices) power down their devices or put them to sleep when they're not in use. Less obvious, perhaps, is that users in remote data centers often do the same thing with their servers and desktop PCs. Not a monumental issue, but one that must be addressed.

The next challenge is at the other end of the spectrum: some users leave their computers on -- and apps open -- 24 hours a day. So any viable remote backup system must address the issue of open (and possibly changing) files.

Finally, there's the requirement for bare-metal recovery. In the corporate data center, there are plenty of alternatives when a piece of hardware fails, such as a quick swap of an already-imaged drive. The best alternate a remote user may have is a WAN connection with a decent download speed and the hope that someone from corporate IT is available. If your remote servers or laptops have on-site service, the vendor can replace the hard drive or any other broken components. But then you'll need some type of automatic recovery that requires only the most basic steps (e.g., inserting a CD and rebooting).

Remote and mobile backup solved

The

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typical way the remote bandwidth challenge is solved today is by using a block-level incremental-forever backup technology. The key to backing up over slow links is to never again transfer data that has already been transferred. Full backups are no more and even traditional incremental backups transfer too much data. You must back up only new, unique blocks.

Latency is a separate issue. Just because a product does block-level incremental backups doesn't mean it was designed for use as a remote application. You need to ensure that the backup software understands it's communicating over a remote connection and avoids "roundtrips" whenever possible. Even if you have a remote connection with enough bandwidth, the latency of the connection can severely hamper your backup performance if your backup software isn't prepared for it.

Dedupe does it all

The technology that most people have adopted to solve many of these problems is data deduplication, which significantly reduces the number of bytes that must be transferred. A dedupe system that's aware of multiple locations will only back up bytes that are new to the entire system, not just bytes that are new to a particular remote or mobile location. So if a file has already been backed up from one laptop and the same file resides on another laptop, the second instance of the file won't be backed up.

There are two basic types of deduplication: target deduplication (appliance) and source deduplication (software). Target deduplication appliances are designed to replace the tape of standard disk drives in your existing backup system so your backup software sends backup data to the appliance that dedupes the backups and stores only the new, unique blocks. Using a dedupe appliance has an added benefit, as switching from tape to disk as your initial backup target will likely increase the reliability of remote site backups.

This was first published in March 2011

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