Virtual Tape Library: Key to Business Continuity (Pt. 1)

Virtualization continues to grow in popularity as it offers different ways of backing up our data, in addition to being able to ensure that business-critical systems remain online in the event of an emergency.

Some people have even hailed virtualization as the next frontier of computing. But what is “computer virtualization” and how can you or your clients benefit from it? Let’s take a step back and first review what virtualization is and how it works.

Virtualization 101

Virtualization is a method of running other software or hardware applications under a host system. The virtual system and the host system share the same hardware. Virtualization allows multiple systems to share one physical computer. For example, an enterprise could invest into a computer system with high processing power and maximum memory, then by using virtualization, an administrator could have three or four operating systems running on that equipment (depending on the processing power of the equipment and the operating system requirements). The benefits of hardware cost savings alone justify you or your client's attention to this exciting technology.

Virtualization doesn't stop with operating systems; you can also have virtualized applications and SAN storage pools. In line with these virtualization concepts, presenting storage components like hard disk drives as tape hardware is known as a virtual tape library, or VTL.

How does a VTL work?

VTL technology boasts a high percentage of return on investment, offers ease of installation within an existing archival environment, and affords faster data restores. Additionally, VTL doesn't mean the end of the investment that has been made into physical tape machines or libraries. The architecture of the backup system can still stream data to a physical tape for offsite storage.

In a nutshell, VTL utilizes hardware and software solutions for redirecting the backup data that would have been sent to the tape library to a large RAID array. The backup software is able to do this (by means of hardware and software) by recognising the RAID array as a tape drive. Traditional backup options, such as Full, Differential, Incremental, and Snapshot schemas still function in the same way in a VTL. Essentially, the backup process in place pre-VTL implementation will still be available after migrating to a VTL setup.

Storage concepts of a virtual tape library

The storage concepts of a virtual tape library revolve around streaming backup data to a RAID 0, or RAID 5 configuration. There are several advantages to streaming the data to a disk array first; the principle among them being speed. Benchmark tests have shown that the transfer throughput (from server to backup disk array) is noticeably increased. This is because the data transfer to magnetic tape media is eliminated. Additionally, retrieval of archived data is also much faster because there is no bottleneck due to rewind and fast-forward operations, or of cataloguing tape archives and sessions.

Storage for a VTL system can start at the half terabyte range and go into the hundreds of terabytes depending on your needs. Storage can be high performance Fibre Channel or iSCSI systems. Alternatively, SATA (Serial ATA) and PATA (Parallel ATA) systems are available and are usually lower in cost. All of these storage systems are a good choice for VTL implementations.

VTL software and hardware also support multiple virtual tape libraries. Historically, in environments using a traditional physical tape machine employing one physical tape machine setup, it was noticed there was a lot of data moving to that one device. To address this data movement issue, IT administrators added multiple tape machines, large tape libraries that employ many tape machines, to spread the workload out and to keep the data transfer balanced. VTL setups offer the same multiplicity of backups running at once, which means you can distribute the archiving process over a greater number of data areas. Despite the virtualization, however, the data will still be physically stored on the RAID storage array.

For IT environments that have specific policies regarding offsite storage of data, nearly all VTL systems now support a physical tape library that is connected to the VTL, allowing a consistent flow of archived data to be "re-archived" onto a physical tape—a backup of a backup. This helps to doubly ensure that user files are being protected. The secondary archive is set to a schedule where tapes can be stored or recycled.

Some organizations have produced a VTL setup on a WAN scale. In theory, this enables organizations to host a remote Disaster Recovery site as little as 50 miles away. By utilizing point in time snapshots in conjunction with such a VTL setup, the data restoration during an outage is reduced considerably.

A large number of tape backup applications already employ some sort of tape virtualization. If you have specific requirements in this regard, you should contact your software vendor. So how does the entire system work?

We answer this question in the second part of this article and explain then, how a data recovery of such a system is done, too. Until then…