Virtualised tape library - the silver bullet of business continuity?

19 April 2016 by Milagros Gamero

Virtualisation 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 virtualisation as the next frontier of computing. But do you know what is computer virtualisation and how can you or your clients benefit from it? Let’s take a step back and first review what virtualisation is and how it works.

Virtualisation 101

Virtualisation 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. Virtualisation 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 virtualisation, 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 (to find out more about storage options for your business, check out this article on cloud-based virtualisation services).

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

How does a virtualised tape library 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 utilises 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 VTL 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 virtualisation, 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 organisations have produced a VTL setup on a WAN scale. In theory, this enables organisations to host a remote Disaster Recovery site as little as 50 miles away. By utilising 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 virtualisation. If you have specific requirements in this regard, you should contact your software vendor. So how does the entire system work?

Make it flow

Operationally, the environment does not change and the scheduled backups still happen as they have already been setup. The hardware and software setup may require some installation depending on the equipment installed, with connectivity details, (IP, SCSI, iSCSI, Fibre Channel) dependent on the topography of the network.

With more setup and configuration a more dynamic, a fault-tolerant solution can be installed—all without the overhead, media cost, and tape recycling schedules.

The image to the right represents one example of a VTL configuration. What exactly does virtualisation bring to this configuration? Virtualisation has the potential to remove tape media from the topography completely.

As mentioned previously, products are available that can create multiple virtual libraries or tape machines. The advantage is that multiple backups can be running from different servers all into the same storage pool. This storage can perform a less rigorous backup to tape, or another VTL. This second level VTL can be slower disk storage and function as an ongoing backup of the first level backup. Easy availability of products to facilitate creation of VTL environments along with affordable technology has made the dual backup process with different schedules possible.

Data recovery of virtual tape library storage

Today's compliance and regulatory laws are requiring organisations to ensure 'data availability.' You won't get an understanding nod from an auditor by saying, "The server you wanted to look at has just failed." What happens when there is a failure on the storage array that is hosting your first level or second level backup data?

All is not lost! A professional data recovery firm can rebuild and extract the data from storage arrays that are used in VTL systems, focusing on the data contained within the tape archive files post-extraction. Today's complex archiving software will store the target files with a high compression ratio and internal cataloguing method.


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