Agentless backup software, such as Asigra Inc.'s Televaulting and Chief Applications Israel Ltd.'s Backup prOxy Server (BOS), backs up systems without the need to install software (agents) on each system that is being backed up. The backup is handled by a server attached to the network. With Asigra, servers at remote locations preprocess the data and send it to a central site for storage.
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Note: VMWare Inc.'s consolidated backup is agentless, but it isn't quite the same thing. For one thing, it only handles VMWare virtual machines -- for another, it isn't a backup product. According to VMWare, its purpose is to enable backup software to back up virtual machines as painlessly as possible.
Decide what to back up
One of the most important steps in agentless backup is deciding what you need to back up. Being selective will greatly reduce the load on your WAN and system resources in general.
There's an added incentive to prune your data with BOS and Televaulting; both companies' pricing model is based on how much data the software processes. In the case of Televaulting, that's how much data is actually stored on the central server. In the case of BOS, it's how much data the software handles.
Of course, if you're talking about hundreds of systems at multiple locations, pruning the data intelligently can be difficult because it's hard to set effective backup policies for all those systems.
One strategy is to divide the sites to be backed up into tiers and sample each tier to get an idea of what's out there. Eran Farajun, executive vice president of Asigra, says that some of the large clients who use his company's Televaulting software have as many as seven tiers because of the variations in the sites to be backed up. By sampling each tier, the administrators were able to form a picture not only of what data was on the sites that needed to be backed up, but also to get an estimate of how much data was involved in each class of sites. With that information, he says, the customers can estimate their bandwidth requirements.
Estimate your bandwidth
When backing up from multiple remote locations it's important to know how much data you will be transmitting to the central server and to be sure that you have enough bandwidth to handle the load.
In making the calculation, you have to take into account any deduplication or compression done on the data before it is transmitted. Often the size of the images for backup is considerably larger than the amount of data that is actually going to be transmitted. Asigra provides a simulation tool to help customers estimate their bandwidth needs. The tool runs simulated backup sessions on a remote site, complete with the deduplication and compression steps, and reports on the size of the files to be transmitted.
Make sure you're secure
Authentication is a special concern for agentless backup. This is especially true of remote agentless backup, as the data will travel over the Internet or a WAN.
Because there is no agent on the target systems, the backup software needs passwords and account names to log on to each system. Further, it needs to be able to access all the data to be protected on each box.
If the passwords and other access information are encrypted, you also need effective key management in place to handle the keys for every machine being backed up. This includes keeping a backup file of keys, also encrypted, on an administrators' machine so the information can be recovered if something happens to the site's key files.
About the author: Rick Cook specializes in writing about issues related to storage and storage management.
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