Virtual tape library (VTL) technology has been around for many years and was once exclusive to the mainframe domain. Now available from numerous vendors with support for the most popular operating systems (including Linux for some) and data backup applications, VTLs can emulate many tape devices such as LTO, DLT, 9840, etc.
Some of the larger appliances can be subdivided into more than 100 virtual libraries, with well over 1,000 virtual tape drives and more than 8,000 virtual tape volumes. The size of these appliances can take as little space as a 1U rack, intended for SMBs, or as much as an entire server rack and more for the enterprise.
Thanks to the popularity of data deduplication and the competition in that space, VTLs have become much more affordable and are now offered in sizes (and prices) that are much more appealing to the SMB space. But before rushing to call your favorite vendor, ask yourself a few questions. There are some good reasons for wanting to deploy a VTL, but there are also some not-so-good ones.
Some of the good reasons:
- Tape virtualization allows you to take advantage of disk-based backups without actually having to purchase new backup software. The virtual drives will look like regular tape drives to most backup software.
- You can pretty much eliminate onsite tape media handling. Many smaller organizations simply do not have the resources available to change tapes. This is also very common for remote offices with no technical skills onsite.
- When the VTL offers remote replication capabilities, you can eliminate all offsite tape media handling, which can be a blessing for remote offices or smaller companies using a collocation service provider.
- If you have made a significant investment on a tape subsystem, you can use VTL for onsite backups and physical tapes for vault or archives.
Some of the not-so-good reasons:
- You will not save significant amounts of money and, in most cases, you will end up spending more with a VTL. Many vendors have developed sophisticated ROI tools that promise significant savings when compared to tape, often by using unrealistic media handling and storage costs. But the reality for most SMBs is that gigabyte for gigabyte, tape is still cheaper than disk.
- You have very long backup data or archive retention policies. If your IT staff routinely removes tapes from a small library to make room for empty tapes because some backups have to kept for a long time, your VTL might run out of capacity. Entry-level VTLs have finite capacity and are priced accordingly. When you run out of capacity on these units, your options are limited to deleting data or buying an additional unit. Capacity is not addressed by simply purchasing media as is the case with tape.
Porting VTL technology to open systems was a great advancement in the data protection field. It enables the reduction of media handling, management and physical storage. It also provides an added layer of protection against tape loss. It can replace extra backup resources or become a remote extension to an existing infrastructure. That said, tape virtualization is not a quick fix to a poorly designed backup environment, and it does not address the absence of clearly defined data backup policies. And no matter what anyone says, even if RAID 6 disk is more reliable than tape, it is still not a disaster recovery strategy.
About this author: Pierre Dorion is the data center practice director and a senior consultant with Long View Systems Inc. in Phoenix, Ariz., specializing in the areas of business continuity and disaster recovery planning services and corporate data protection.