Ditch the Tape
Four years ago, the city of Tucson faced a dilemma. The backup needs of the government's most critical agencies, including police, fire and urban planning, were growing at a rapid clip, but the physical tape system could not handle the increased demands.
"The backup window for these important applications was running over 12 hours and, therefore, spilling over into the workday and affecting network performance," says Chris Ferko, network services IT manager. He also battled failed drives and corrupt backups.
To alleviate the strain and shorten the backup window, Ferko 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. They enable IT 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.
Tucson's two 8 terabyte HP StorageWorks 6000 Virtual Library System devices, which Ferko uses to back up his Windows and Novell servers, enable him to continue to use the tape management processes he established using his Symantec Veritas NetBackup software. The disk-based system has enabled him to reduce his nightly incremental and weekly full backup windows for the city's 70 servers to less than four hours.
Source: Enterprise Strategy Group
Although Ferko uses the VTLs as secondary storage and then backs up data to tape once a month for continuity of operations, Connor says many IT teams have found that they don't need their physical tape libraries anymore because the VTL can hold enough data. Others, such as the state of Ohio, have chosen to share data between two VTLs -- one on site and one offsite -- for more efficient business continuity and disaster recovery.
Lyle Fast, system programmer for Ohio's Department of Administrative Services, says his site-to-site setup has enabled him to triple his storage capacity compared with the state's previous tape library. "We now can offer the 12 agencies we serve quicker restores and file retrievals. We also can back up a lot more of their critical data," he says.
The VTLs, which are a target of the department's IBM Tivoli Storage Manager software, have also allowed him to increase capacity and gain higher storage reclamation rates -- plummeting from 66 percent of space taken up by expired data to 33 percent.
Some VTL users have found that new 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.
The Ohio Department of Administrative Services didn't require deduplication when purchasing its VTL because it does not work well with client compressed and encrypted data. But that hasn't soured Fast on VTLs overall. Instead, he says the technology has enabled him to expand his nightly backups from 1 TB to 3 TB. "The VTL has certainly allowed us to do that more easily than tape ever would," 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 off site 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 de duplication.