Virtual Tape Library
A wide range of technology solutions are currently available for backup targets. Tape and Disk libraries are the two most commonly used backup targets. In the past, tape technology was the predominant target for backup due to its low cost. But performance and management limitations associated with tapes and the availability of low-cost disk drives have made the disk a viable backup target.
Tape backup provides the ability to copy data packages from a hard drive to a tape cartridge for storage, backup and recovery purposes in the event of a computer crash or other failure. Conversely, disk backup entails copying data and other information onto a hard drive for easy access later on.
A virtual Library(VTL) is one of the options that uses disks as a backup medium. VTL emulates tapes and provides enhanced backup and recovery capabilities.
Virtual tape library : A disk-based backup system, a Virtual Tape Library(VTL) emulates physical tapes. A VTL has the same components as that of a physical tape library, except that the majority of the components are presented as virtual resources.
- A virtual tape library appliance offers a number of features that are not available with physical tape library. Some virtual tape libraries offer multiple emulation engines configured in a active cluster configuration. An engine is a dedicated server with a customized operating system that makes physical disks in the VTL appear as tapes in the backup application. With this feature, one engine can pick up the virtual resources from another engine in the event of any failure and enable clients to continue using their assigned virtual resources transparently.
- Virtual tape libraries (VTLs) ingest data over a Fibre Channel interface, which enables seamless integration with many existing backup infrastructures and processes. However, most backup software supports direct backup to disk over standard file protocols such as Network File System (NFS) and Common Internet File System (CIFS), eliminating the requirement to emulate tapes.
- More than 85% of enterprises around the world now operate in hybrid multicloud environments, and in the next few years nearly all will move to these architectures. At the same time, mainframe utilization has remained robust — IBM Z mainframes process 30 billion transactions each day, including 87% of all credit card transactions on the planet.
- These major technology trends all point to one important conclusion — more companies than ever before need economical mainframe-optimized, tape-based data storage solutions that can help them leverage the advantages of the public cloud.
How VTL Works?
Virtual tape library use disks as backup media. Emulation software has a database with a list of virtual tapes, and each virtual tape is assigned space on a Logical Unit Number(LUN). A virtual tape can span multiple LUNs if required. Similar to a physical tape library, a robot mount is performed when a backup process starts in a virtual tape library. However, unlike a physical tape library, where this process involves some mechanical delays, in a virtual tape library it is almost instantaneous. Even the load to ready time is much less than in a physical tape library.
After the virtual tape is mounted and the tape drive is positioned, the virtual tape is ready to be used, and backup data can be written to it. Unlike a physical tape library, the virtual tape library is not constrained by the shoe shining effect. In most cases, data is written to the virtual tape immediately. When the operation is complete, the backup software issues a rewind command and then the tape can be unmounted. This rewind is also instantaneous. The virtual tape is then unmounted, and the virtual robotic arm is instructed to move it back to a virtual slot. The steps to restore are similar to those in a physical tape library, but the restore operation is instantaneous. Even though virtual tapes are based on disks, which provide random access, they still emulate the tape behavior.
Traditional VTLs can only provide a front-end, fast cache to a tape library infrastructure, temporarily alleviating backup window problems. These systems can’t cost-efficiently retain backup data for any length of time, and backup data is too large to be replicated or “vaulted” over a wide area network (WAN). They don’t offer an evolution from tape and its associated challenges so that, ironically, tape remains the primary method of retention, recoverability, and disaster protection.
However, EMC Data Domain VTL software eliminates tape-related failures by enabling all EMC Data Domain systems to emulate multiple tape devices over a Fibre Channel interface. Data Domain VTL software emulates up to 64 virtual tape libraries with up to 540 linear tape-open (LTO)-1, LTO-2, or LTO-3 virtual tape drives. VTL software provides up to 64,000 virtual slots and an unlimited number of virtual tape cartridges, with the ability to dynamically change the number of virtual slots and cartridge access ports.
Benefits of a VTL
- The ability to easily integrate with an existing Fibre Channel or tape-based infrastructure is the main benefit of a VTL. Data Domain VTL software is qualified with leading open systems and IBM enterprise backup applications, easily integrating into existing Fibre Channel storage area network (SAN) backup environments.
- Data Domain systems simultaneously support data access methods through VTL over Fibre Channel, remote Network Data Management Protocol (NDMP) access over Ethernet for network-attached storage (NAS), Network File System (NFS) and Common Internet File System (CIFS) protocols over Ethernet, and EMC Data Domain Boost. This deployment flexibility along with simple administration means that users can rapidly adjust to changing enterprise requirements.
- Improved backup and restore times, Reduced tape media handling, Multiple backup jobs can be done simultaneously, Data compression, No Performance and capacity limitations.
- If required Virtual Tapes can be restore back into Physical tapes.
Here are some references:
- https://www.delltechnologies.com/en-in/learn/data-storage/virtual-tape-library.htm
- IBM TS7770 Virtual Tape Library Manual
- Book: Information and Storage management v.3
