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Virtual tape libraries: Old backup technology holdover or gateway to the future?

Virtual tape libraries are still alive and well in data backup environments, despite the popularity of disk-to-disk backup.

Virtual tape libraries (VTLs) have established themselves as an important adjunct to tape. Perhaps because of that lineage, and the growing movement away from tape as a first tier backup option, VTLs have something of an image problem. "Some people don't want to talk about VTLs. There is a myth that it is an old tech or that VTLs are dead," said Greg Schulz, founder and analyst at StorageIO Group. But in fact, Schulz, analysts and users said VTLs are very much alive and remain a vital part of the data backup infrastructure.

Among the believers is Chris Mohr, a network analyst at Pinnacle Health, a nonprofit hospital located near Harrisburg, Penn. His organization manages approximately 40 TB of data storage in total running across an EMC Corp.-based storage area network (SAN). That infrastructure was supplemented a few months ago with a FalconStor Software VTL. Because the VTL has data deduplication, offering up to 20:1 compression ratios, the actual "landing space" is only about 8 TB -- plus another 8 TB to handle the dedupe activity. But that's enough to handle almost all of Pinnacle Health's 40 TB of storage.

Not surprisingly, because writing to disk is much faster than writing to tape, Mohr said his VTL has significantly improved backup performance. For disaster recovery, Pinnacle Health still writes from VTL to tape and sends those tapes off-site for storage. "We acquired the VTL because we wanted more reliability. We found that tape drives can misbehave sporadically. There were also issues like cleaning and tapes getting damaged," he said. Although Mohr admitted that he continues to learn the "nuances" of the VTL, one of its strengths has been the fact that he did not have to "retool" backup procedures. "It fit right into the operation and the person who attends the tapes didn't have to get retrained," he said. "It was just so easy to implement, we could interface right away and end users didn't have to learn anything new because CA ARCserve is still the front end," he added.

Virtual tape libraries help reduce backup windows for the U.S. Army

Another virtual tape library fan is Gary Horsley II, a senior system engineer at the U.S. Army's Surface Deployment and Distribution Command (SDDC), an organization that supports more than 90% of Department of Defense equipment around the world using a mixture of commercial and military services. The organization employs about 5,000 people nationwide, including eight IT staff at Scott Air Force Base in Illinois to cover backup, storage, server services and networking.

It made an incredible difference and we are now planning to purchase another VTL to double our capacity.

Gary Horsley II
senior system engineerU.S. Army's Surface Deployment and Distribution Command

Like Pinnacle Health, SDDC was having trouble with backup windows. As SDDC's needs grew, Horsley said it turned out to be difficult to expand the tape library. "We found we were running out of backup space as well as backup windows -- they were getting too long and running into the next day," he said. Because growth was expected to continue, SDDC started looking for a scalable alternative. "Naturally, we went to a disk-based backup that gives you faster backup time and multiple paths, then, we offloaded to tape for offsite backup and disaster recovery," he explained. They selected Quantum Corp.'s DXi7500, a disk-based deduplication and replication solution for use as a VTL and network-attached storage (NAS) while relying on a Quantum Scalar i500 tape library for long-term retention and archive. The immediate result was that backups went from eight hours down to just 20 minutes.

"It made an incredible difference and we are now planning to purchase another VTL to double our capacity," he said.

Users see bright future for VTLs

Perhaps the ultimate virtual tape library "power user" is Walt Thomasson, managing director of Rentsys Recovery Services, a backup and recovery services business. Headquartered in Dayton, Ohio, with several data centers located around the U.S., the company has adopted FalconStor-based VTLs as a service offering for its customers.

According to Thomasson, the backup industry has often focused on providing customers with hot sites -- a central location they can migrate to and reestablish operations. Rentsys takes an alternative approach, combining tools and technology to provide locally oriented recovery ability. For example, Rentsys maintains a large inventory of hardware for immediate shipment and has a fleet of mobile trailers preconfigured as offices, call centers or data centers that can be brought to a customer site on short notice.

Thomasson said VTLs were a natural addition to these tools. "We found that we had a very good recovery capability but when our clients would ship us whole pallets full of tapes -- it was taking up to two weeks to rebuild using our existing technology," he said. By adopting the FalconStor VTL, which runs on standard servers that Rentsys owns anyway, it was possible to shrink client recovery time dramatically. Now, by using a VTL and its built in-dedupe capability at the client site, Rentsys has reduced the number of tapes required. Then when a client needs to restore data, Rentsys can ship a VTL to them preloaded with all the data," he explained. Rentsys even brands the offering as Flexdata.

Above all, Thomasson sees a bright future for VTLs. "I see nothing in our market that would indicate a downturn for VTLs. As a recovery technology, for the money -- especially when it is combined with dedupe -- there is nothing close," he said. In fact, Thomasson said he thinks VTLs my just be starting to get established. Just as virtual server technology took time to "catch on" he predicts that VTLs will further increase in acceptance. "In my view VTLs are an alternative to high-availability systems at a fraction of the cost. We have done this calculation and we see companies that adopt VTL potentially saving millions of dollars," compared to the cost of high-availability systems and the cost of traditional all-tape backup, he added.

VTLs bridging the gap between tape and disk backup

StorageIO's Schultz said the fact that companies have to retain more data for longer periods provides an opportunity for VTLs. "Tape is shifting from its role in backup and rapid recovery to a focus on retention. So, VTL is becoming more relevant," he said.

"I think people get hung up on the word tape. If it were just called a virtual library it might sound better," he said. In fact, he argued, VTLs shouldn't be thought of just as an adjunct to a tape library because some dedupe devices that can present themselves as a tape drive or file system fall under the umbrella of VTL. So VTL is really about an emulation mode.

Beyond nomenclature, the fact remains that companies have to bridge the gap between old (pure tape) and new technologies and virtualization in the form of the VTL is the bridge. "It makes the new look old so you can fool the old software and processes while leveraging new technology so you buy yourself some time and you can then rethink you architecture for the long term," Schultz said.

While offering some similar sentiments, Lauren Whitehouse, a senior analyst at Enterprise Strategy Group, takes a position on VTLs that is somewhat more nuanced. For instance, while agreeing that data retention requirements are a VTL driver, she pointed out the many variations within industries and regions. "It depends on which regulations have to be followed to determine what policies, media type, etc. have to be enforced." And there are disk targets that have a WORM lock feature to make sure data is in an unalterable state, but those newer technologies don't always meet every aspect of retention requirements. "For the most part, IT is still comfortable with tape media for long-term retention … unless, of course, they have an active archive solution that might be better suited to their needs," she said.

For now, VTL is still central -- but disk storage is evolving. Vendors such as Quantum and Data Domain (recently acquired by EMC) have products with both VTL and file interfaces available in their storage systems. FalconStor has two independent products -- one a VTL interface (FalconStor Virtual Tape Library) and the other with a file interface (FalconStor FDS). "Most recently, long-standing VTL vendor Fujitsu introduced a file interface solution and others have a file interface on their roadmap," she noted.

Finally, Whitehouse offers the summation provided in the recent ESG report she authored: "ESG believes the [VTL] category will face mounting pressure from competing disk backup technologies, apathy regarding physical tape-only backup methods, financial challenges, and more. These combined trends suggest that virtual tape libraries will remain a key enabling technology for some -- but not all -- backup environments and, over time, may eventually simply fill niche requirements for select organizations."

Offering a last word on the subject, David Hill at Mesabi Group said, "Even though VTLs have been around for a number of years now, enterprises are still thinking through all the issues related to their backup redesign." For example, data deduplication is a hot topic, but exactly how should IT do data deduplication? Hill said some organizations have made up their minds and decided what to do -- the early adopters. Many others will think about it for a long while, "but, in a lot of cases, I think that many companies are still contemplating what they are going to do -- and VTLs may be part of the answer."

About this author: Alan Earls is a frequent contributor to SearchDataBackup.

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