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Friday, 29 April 2022 11:44

The advantages of virtual tape library VTL in practice

By Vital Shpakouski

GUEST OPINION:  Today, information is one of the main engines of business, because the very existence of a company sometimes depends on the ability to store and process it. In this article, we will talk about new technologies for reliable data storage, which is so necessary for modern business.

Modern data storage systems (DSS) provide an exceptionally high level of storage reliability due to fault-tolerant hardware architecture, including component duplication, support for RAID mechanisms, etc., as well as through the use of data copying, snapshots, and replication. However, no matter how reliable the storage infrastructure is, the backup and recovery system is still an indispensable component of a modern data processing centre (DPC).

As an optimal solution that incorporates all the advantages of the disc-to-disc concept and, at the same time, is devoid of the disadvantages of tape libraries, leading manufacturers of data storage systems suggest using virtual tape libraries (VTL).

What is it and what are its advantages?

Virtual Tape Library (VTL) is a disc-to-disc data backup solution that emulates traditional tape libraries. From the point of view of the backup application, the virtual tape library looks like one or more conventional libraries, allowing the VTL to quickly and seamlessly integrate into the customer's existing infrastructure.

VTL virtualizes disk space into tape space and can implement the same functionality as a traditional tape library in traditional backup software. At the same time, a virtual tape library backup has a number of advantages over a tape library:

  • seamless integration;
  • data deduplication;
  • low cost (with a small amount of data);
  • higher level of reliability for data safety;
  • high speed of saving, and restoring data;
  • ease of random access.

Simply put, the main advantage of VTL is to replace the tape with a hard disk, which is faster, more stable, and compatible. Let's consider these features in more detail.

Seamless integration

The key advantage of virtual tape libraries over disc-to-disc solutions lies in the ease of implementation. In VTL solutions, access to drives, management systems, cartridges, etc. is carried out in exactly the same way as when working with a real tape library.

Most modern virtual libraries allow you to emulate various types of magnetic tapes and are compatible with all popular backup applications such as EMC Legato Networker, HP Data Protector, IBM Tivoli Storage Manager, etc. Due to this, the introduction of VTL does not require significant changes in the existing procedures and policies of the RMS. This approach protects previous investments in storage infrastructure and also reduces the risk of RMS failures during the transition from tape-based to disk-based backup.

In addition, unlike D2D solutions, VTL allows you to efficiently use the disk resources of the array. All capacity is available as single storage that emulates the required number of drives and tapes of arbitrary capacity.


Data deduplication

The second most important advantage of VTL is the possibility of data deduplication. Deduplication technologies provide multiple reductions in the amount of stored data by identifying duplicate data that has already been stored earlier.

Depending on the specifics of the backed up data, and the frequency and intensity of their changes, the effective (provided) storage capacity can exceed the physical volume of the disk system by dozens of times. This approach radically reduces the requirements for the capacity of a disk array, and the cost of its acquisition and operation, which significantly reduces the cost of creating and storing data backups.


Deduplication makes storing backup data cheaper on disk than on tape. It drastically reduces the disk capacity requirements of the arrays used to store backup data. Consequently, the cost of storage is also reduced.

With a deduplication ratio of 10:1, the total cost of storage on disks and tapes is practically equal, and, for example, when a deduplication ratio of 15:1 is reached, the VTL solution becomes the undisputed leader in this indicator. Therefore, it is the degree of data deduplication that most often becomes an object for “manipulation” by marketers of manufacturing companies. Some manufacturers, declaring the implementation of a deduplication degree of 100:1 or even more in their solutions, often talk about “idealized” situations that are far from always possible in real conditions.


Data security

The use of disk arrays as a storage medium for data backups brings additional features to the RMS to ensure disaster recovery. Thanks to the solutions offered by some manufacturers, the user can install two virtual libraries - in the main and backup computing center and organize data replication between them, using SAN or IP networks as data transmission channels.

This approach eliminates the risks that inevitably arise when unloading, transporting, and storing tapes in remote storage. In the event of a disaster, the backup storage switches to the main mode and is used to restore data to both the backup and the main site.

Data recovery speed

An important argument in favour of the VTL solution is the speed of data recovery from remote storage. Depending on the bandwidth of the communication channels and the amount of data transferred, recovery time can be measured in minutes versus hours or even days required to find and deliver the tapes required for recovery.

The use of VTL can significantly reduce the backup time, however, this depends on the system architecture, the nature of the servers and clients, as well as the specifics of the data being backed up.


Ease of random access

The use of backup to disks allows you to minimize the time to restore data from a backup. Unlike tapes, which only support sequential data access, disks support random access. This allows faster recovery of small amounts of saved data, such as a few mistakenly deleted files. Since no time is required to search, load, and rewind the tape, the delay before the start of reading (restoring) data in the case of a disc-to-disc system is measured in milliseconds versus seconds and even minutes for tapes.

Moreover, since the backup system writes data to tape as an image, if a single file needs to be restored, the CRP will have to read the entire image before it finds the required file. Systems based on hard disks do not have this drawback and allow you to restore any amount of data almost instantly.



Based on the foregoing, we can say that the use of VTL solutions can be justified both in large backup environments and in the RMS of small data centers. VTL can completely replace traditional tape libraries and eliminate a number of problems with their implementation and operation. 

Particularly interesting in this case are solutions that allow sharing the resources used to store backups of a disk array with other servers and applications. This approach allows you to maximize the efficiency of the use of equipment, and in addition, to achieve significant savings in the administration and support of the backup and data recovery system.

About the author
Vital Shpakouski
Vital Shpakouski: Philologist with higher education, professional translator, former volunteer and teacher, entrepreneur, and salesperson with 13 years of experience. Now a copywriter in the field of Internet marketing, helping businesses create useful content and promote their products. I write on various topics, from business, fintech, web design, and software reviews to self-development, travel, and health. In my free time, I create music and songs that no one hears and take photos and videos that no one sees.
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