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Is Disk Backup Green?

11:00 AM -- Are you kidding me? How can adding disk to a tape-based process be green? Tape is one of the ultimate green technologies. When not in use it sits quietly on a plastic shelf in a library or in a vault somewhere. How can de-duplication possibly be "green"?

First, let's face reality. For a variety of reasons, most users are adding disk to their backup strategies. Right or wrong, it is happening, and I don't think it's going to stop. The challenge is that adding disk in almost any form -- yes, even MAID (massive arrays of idle disks) -- is going to require additional power consumption when compared to backing up to tape. So there is a balance to be struck: how to add disks to get the improvements to the backup process that it offers without requiring a new power grid.

There are two technologies that are going to vie for your green attention: de-duplication and MAID. We'll get to MAID later, but first let us examine de-duplication as the "greener" alternative to standard disk. The basic idea is that you are going to require less disk capacity up front and significantly less capacity over time to store backup jobs with de-duplication.

With all de-duplication, your first full backup is going to have the most impact on capacity. Most users will pick up some optimization because of de-duplication and compression, but the capacity savings are not as significant as the subsequent full and incremental jobs will be.

The type of de-duplication that your system uses will also affect power efficiency. Here we don't get in to the inline vs. post-processing debate again, but focus on the differences of how your system chooses to implement post-processing. If you are declaring greenness based on storage efficiencies, then you need to deliver as much optimization as possible throughout the process. The issue is how much native capacity you need prior to the de-duplication process occurring.

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