Low-cost disk backup vs. tape

Learn how two low-cost approaches to disk backup – power-managed disk and deduplication appliances – can enable your customers to lessen their reliance on tape backup.

In a recent story, we looked at cloud-based backup as an alternative to tape drive autoloaders for SMBs. But what if you can't get your customer to the cloud? Are disk backup devices a viable alternative to autoloaders?

To determine the answer to that question for your customer, you should first examine why they're considering a tape drive autoloader. In most cases it's because they're backing up their data to a single tape drive but are getting to the point where they can't fit their backups onto a single piece of media; so, they want to automate the process of putting new tapes in the drive during the backup process, generally overnight when there's no one in the office. They might also have tried disk backup of some sort, possibly just by copying data from one hard drive to another rather than using a device designed for the task.

Either way, the common denominator is that they've been backing up data in a nearly manual way but now need to automate the backup process; a tape drive autoloader seems to be the obvious and logical choice. Comparing costs between tape and disk backup may seem to underscore that choice. And it's true: Many disk-based solutions cannot compete with tape drive autoloaders on price. As we explained in our last story on this topic, a tape drive autoloader that can hold about 4 TB of data would cost about $8,000.

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But there are relatively inexpensive approaches to disk backup that make it more competitive cost-wise with tape backup. This is where you need to step in and educate customers on the options, and there are two good ones for low-cost disk-based backup. For instance, they could back up data using a power-managed disk array (MAID) solution like those offered by Nexsan. Or, you could suggest a Data Robotics Drobo system and populate the unit with power-managed drives. While neither unit handles deduplication, they do have MAID capabilities that allow the unit to power down when not in use. This means customers could have a large disk target that doesn't need to be powered on or off. Most backup applications have at least basic support of disk as a backup target so simply attaching a power-managed disk can be an inexpensive (about $6,600 for a 4 TB system, or $14,000 for 14 TB), power-efficient and viable alternative to a tape library.

The other option is a deduplication-capable disk backup unit; both Data Domain and ExaGrid Systems have such systems for SMBs. Deduplication allows a customer to buy significantly less disk and store backup data on disk for a longer period of time by eliminating redundant components of the backup set. Most customers will see little change between the first full backup and the next, and a deduplication appliance stores only the changes after the first full backup. This could allow an SMB customer to store months' worth of data on a system with little more capacity than their current total amount. A deduplication appliance providing about 1.5 TB of storage costs about $15,000 (not including support); using a 20-to-1 data reduction ratio, that space would equate to about 30 TB of non-deduped data. (It's important that you understand data reduction rates before you recommend a particular deduplication solution for a customer.)

The only challenge with either power-managed disk or a deduplication appliance is getting the customer's data off-site. While most SMBs don't have a sophisticated offsite storage location, they should still move data to somewhere other than their primary facility, even if it means the data goes home with one of the IT administrators. Whether they're using a power-managed disk or a deduplication appliance, their existing tape system could be used to create a copy that would be transported offsite. Remember the original motivation to consider an autoloader was so that full backups could complete overnight without operator intervention? With a disk-based system, a copy to tape could be made during the day without affecting application performance since it would be a direct move from backup disk. The IT administrator would be there during the day to make the tape swap, and that tape could be transported offsite, whether with one of the IT administrators or via a more sophisticated method.

As an alternative to that scenario, if the customer has a second site, a deduplication approach may be ideal since dedupe appliances can replicate the unique backup data to a second site. While that would require the purchase of a second deduplication unit, for many SMBs that would solve the DR issue almost entirely.

After all is said and done, a tape drive autoloader may be a better choice than disk backup for your SMB customer, but you won't know that for sure until you review all of the potential options with them.

About the author

George Crump is president and founder of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. With 25 years of experience designing storage solutions for data centers across the United States, he has seen the birth of such technologies as RAID, NAS and SAN. Prior to founding Storage Switzerland, George was chief technology officer at one of the nation's largest storage integrators, where he was in charge of technology testing, integration and product selection. Find Storage Switzerland's disclosure statement here.

This was first published in June 2009

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