In this third segment on reducing backup windows, the focus will be on getting rid of the data that no longer needs to be backed up. If you're like most of the customers we speak with, well over 85% of the data that you backup during your full backup hasn't changed since the last backup and 70% hasn't changed in the last few years. Yet, every week, it's methodically backed up. If you could eliminate this data, that means in a 10 TB environment you could reduce your full backup set to 1.5 TBs, or worst case to 3 TBs. That will have a dramatic and positive impact on your backup window.

The secret is archiving. There are two steps to achieve this goal. First, you have to identify and move this data. I went through some of the products that can move data in my entry on Data Keepage. In this entry we will talk about some of the targets available for archiving: Tape, Optical, or Disk.

To determine what kind of archive is best for you, think about what you would use the backup for in this new model. In most cases, 99% of the time you should be using your backups to recover the most recent copy of something; a deleted file or corrupted database, for example. Anything beyond the most recent copy should be in the archive. Then think about what you would use the archive for in this new model -- basically everything else.

If you think about times you've been asked to do a restore of data that is six months old or older, it was usually a specific piece of information. A key component of archive is search; you must be able to search the archive for an extended period of time. Most backup applications have decent search capabilities but don't hold that metadata information for very long. As a result, old restores become a challenge with backup.

Additionally, you may need to get to that information years, possibly decades, from now. You have to make sure that what you store that data on is going to be accessible, years or decades from now. Think about what you wrote data to 15 years ago ... Windows 95 was the hot OS, we thought the Red Sox would never win the World Series, and we were all complaining about the price of gas being $1.30 per gallon. Our tape backup / archive of choice was tape and it was probably DLT, 8MM, or even DDS formats. While not impossible, reading a DLT or DDS tape from 1995 would, at a minimum, certainly be a challenge, but I think I could do a pretty good job getting data off that Windows 95 box if I had to. Given the choice, I would pick the disk, for sure.

I think the same logic applies to disk as an archive. Disk is easy to access and tends to evolve more slowly from a file system format perspective. It is certainly easier to search for and retrieve information from. If disk can overcome the limitations of, well, disk (scalability, reliability and cost), then it could be the ideal target for these long-term archives and cause a significant and near-permanent reduction in the backup window.

Our next entry will examine the disk-based archive concept to see if it can overcome those challenges.

George Crump is founder of Storage Switzerland, an analyst firm focused on the virtualization and storage marketplaces. It provides strategic consulting and analysis to storage users, suppliers, and integrators. An industry veteran of more than 25 years, Crump has held engineering and sales positions at various IT industry manufacturers and integrators. Prior to Storage Switzerland, he was CTO at one of the nation's largest integrators.