Three years ago, the Fox Chase Cancer Center in Philadelphia faced a dilemma. The center had grown to 300 servers and, in turn, its backup needs were growing at a rapid clip. The physical tape system could not keep up.
“We'd have more than 14 hours of data to back up in a 12-hour window,” says Karl Barth, director of systems and operations at the center, which hosts medical residents and post-doctorate researchers and is affiliated with Drexel University. Barth also battled occasional failed drives and corrupt backups.
To alleviate the strain and shorten the backup window, Barth and his team turned to a virtual tape library (VTL), a disk-based technology that emulates pools of storage as tape-based drives. Virtual tape libraries can be software- or appliance-based and are available from manufacturers such as EMC, Fujitsu, HP, IBM, NetApp, Overland Storage, Spectra Logic, Sun Microsystems and Tandberg Data. VTLs enable IT teams to manage storage as a single entity and run concurrent backups to speed backup and recovery. Rather than mounting and searching through physical tapes, VTLs offer faster and more reliable access to disk-based data.
“VTLs appeal to organizations that are used to dealing with tape, because they offer tape-based functions without having to swap and rotate tapes,” says Deni Connor, principal analyst at Storage Strategies Now. VTLs are also budget savers, she adds, because they eliminate the data center footprint of physical libraries as well as the cost of tapes.
Barth agrees. Fox Chase uses the IBM System Storage TS7650 ProtecTier Deduplication Appliance, which enables him to continue to use the tape management processes he established using his Symantec Veritas NetBackup software. The appliance has reduced his nightly incremental and weekly full backup windows to about six hours.
Source: Enterprise Strategy Group
Although Barth uses the VTLs as secondary storage and then sends data to tape once a month for continuity of operations, Connor says many IT teams have found that the VTL can hold enough data that they don't need physical tape libraries anymore. Others, such as Grand Valley State University in Michigan, have chosen to share data between two VTLs onsite and offsite for more efficient business continuity and disaster recovery.
In fact, Grand Valley relies on four Overland Storage REO 9100 VTLs split between the university's Allendale and Grand Rapids campuses to ensure top-notch failover and recovery capabilities, according to network engineer David Reed. He says the 16 terabyte VTL system lets him run 40 virtual-drive processes, which enables more servers to be backed up in a much shorter amount of time. “We do incremental every night, plus a few differentials. Before, we were only doing differentials,” he says.
Some VTL users have found that newer features, such as data deduplication, have also helped them boost capacity. Data deduplication is a process by which only changed data is stored and is available in two varieties: in-line and post-processing. Connor says the benefit of in-line, which is offered by IBM, is that you don't need extra storage to hold the data while it's checked for duplication. However, in-line processing can affect performance, as bits are checked at the source in real time. With post-processing, which is offered by Spectra Logic, all data is sent over and then examined at the storage target.
Fox Chase's Barth has found data deduplication to be incredibly helpful. “At our peak, we have about 200TB of data. There's no way we could back that up properly without deduplication,” he says.
Barth is also a believer that the VTL has helped him contribute to the institution's bottom line. “The research side of our business depends on grant writing. If a researcher loses or deletes a file and I can retrieve it quickly for him, that puts us one step closer to getting that grant,” he says.
Here are some tips to help you avoid the potential pitfalls of virtual tape libraries:
- If you use replication for continuity of operations, test how long it will take to recover from your offsite VTL.
- Carefully plan out your storage strategy so that if a part of your VTL fails, it does not take down all your critical data.
- Determine whether you are going to destroy old or failed disks yourself or let the vendor take care of them. If you are leaving it to the vendor, make sure your data is either erased or unreadable.
- Don't count on the vendors' estimated volume sizing. Instead, study your own applications and storage needs as well as potential overhead. For instance, there could be more overhead if you're creating lots of smaller cartridges rather than several large ones or if you're using data deduplication.