Virtual tape library

Avirtual tape library(VTL) is adata storagevirtualizationtechnology used typically for backup and recovery purposes. A VTL presents a storage component (usually hard disk storage) astape librariesortape drivesfor use with existing backup software.

Virtualizing the disk storage as tape allows integration of VTLs with existingbackup softwareand existing backup and recovery processes and policies. The benefits of such virtualization include storage consolidation and faster data restore processes. For most mainframe data centers, the storage capacity varies, however protecting its business and mission critical data is always vital.

Most current VTL solutions useSASorSATAdisk arraysas the primary storage component due to their relatively low cost. The use of array enclosures increases the scalability of the solution by allowing the addition of more disk drives and enclosures to increase the storage capacity.

The shift to VTL also eliminates streaming problems that often impair efficiency in tape drives as disk technology does not rely on streaming and can write effectively regardless of data transfer speeds.

By backing up data to disks instead of tapes, VTL often increases performance of both backup and recovery operations. Restore processes are found to be faster than backup regardless of implementations. In some cases, the data stored on the VTL's disk array is exported to other media, such as physical tapes, fordisaster recoverypurposes (scheme calleddisk-to-disk-to-tape,orD2D2T).

Alternatively, most contemporary backup software products introduced also direct usage of thefile systemstorage (especiallynetwork-attached storage,accessed throughNFSandCIFSprotocols overIPnetworks) not requiring a tape library emulation at all. They also often offer adisk stagingfeature: moving the data from disk to a physical tape for a long-term storage.

While a virtual tape library is very fast, the disk storage within is not designed to be removable, and does not usually involve physically removable external disk drives to be used for data archiving in place of tape. Since the disk storage is always connected to power and data sources and is never physically electrically isolated, it is vulnerable to potential damage and corruption due to nearby building or power grid lightning strikes.

History

The first VTL solution was introduced by Cybernetics in 1992 under the name HSTC (high speed tape cache).Later, IBM released a Virtual Tape Server (VTS) introduced in 1997. It was targeted for amainframemarket, where many legacy applications tend to use a lot of very short tape volumes. It used theESCONinterface, and acted as a disk cache for theIBM 3494tape library. A competitive offering from StorageTek (acquired in 2005 by Sun Microsystems, then subsequently by Oracle Corporation) was known as Virtual Storage Manager (VSM) which leveraged the market dominant STK Powderhorn library as a back store. Each product line has been enhanced to support larger disk buffer capacities, FICON, and more recently (c. 2010) "tapeless" disk-only environments.

Other offerings in the mainframe space are also "tapeless". DLm has been developed by EMC Corporation, whileLuminexhas gained popularity and wide acceptance by teaming with Data Domain to provide the benefits ofdata deduplicationbehind its Channel Gateway platform. With the consequent reduction in off-site replication bandwidth afforded by deduplication, it is possible and practical for this form of virtual tape to reducerecovery point objectivetime andrecovery time objectiveto near zero (or instantaneous).

Outside of themainframeenvironment, tape drives and libraries mostly featuredSCSI.Likewise, VTLs were developed supporting popular SCSI transport protocols such asSPI(legacy systems),Fibre Channel,andiSCSI.

TheFalconStorVTL is the foundation of nearly half of the products sold in the VTL market, according to an Enterprise Strategy Group analyst.

In mid-2010s VTLs got a rebirth thanks to hi-capacity "archive" drives fromSeagateandHGSTand more popular "tape in cloud" and Disk-to-Disk-to-Tape (often in cloud) scenarios.

AmazonandStarWind Softwarein partnership withVeeam,BackBlazeandWasabi Technologiesoffer a so-called gateway products that facilitates backing up and archiving "on premises" data as virtual tapes stored inAWS,MicrosoftAzure,Wasabi TechnologiesandBackBlazepublic clouds.The idea is to provide a seamless integration of a backup applications incompatible with the APIs object storages expose. Say, at the timeVeeamcouldn't doAWSS3and can't backup to the deep archive tier withinAzurestill.

See also

• Backup
• Tape library
• Tape Management System
• Disk stagingfor an alternative approach
• Emulation
• Storage virtualization
• Seven tiers of disaster recovery