Virtual Tape Library
Encyclopedia
A virtual tape library is a data storage
virtualization
technology used typically for backup and recovery purposes. A VTL presents a storage component (usually hard disk storage) as tape libraries
or tape drive
s for use with existing backup software.
Virtualizing the disk storage as tape allows integration of VTLs with existing backup software
and existing backup and recovery processes and policies. The benefits of such virtualization include storage consolidation and faster data restore processes.
Most current VTL solutions use PATA or SATA
disk array
s as 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, for disaster recovery
purposes (scheme called disk-to-disk-to-tape, or D2D2T).
Alternatively, most contemporary backup software products introduced also direct usage of the file system
storage (especially network-attached storage
, accessed through NFS and CIFS protocols over IP
networks) not requiring a tape library emulation at all. They also often offer a disk staging
feature: 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.
market, where many legacy applications tend to use a lot of very short tape volumes. It used ESCON
interface, and acted as a disk cache for 3494 tape 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, while Luminex
has gained popularity and wide acceptance by teaming with Data Domain to provide the benefits of data deduplication
behind 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 reduce Recovery Point Objective /RPO and Recovery Time Objective /RTO to approaching zero (or instantaneous).
Outside of mainframe
environment, tape drives and libraries mostly featured SCSI
. Likewise, VTLs were developed supporting popular SCSI transport protocols such as SPI (legacy systems), Fibre Channel
, and iSCSI
.
The VTLs currently being adopted by Open Systems (including AS400 series) are dominated by FalconStor Software Inc.
The FalconStor VTL is the foundation of nearly half of the products sold in the VTL market, according to an Enterprise Strategy Group analyst.
Computer storage
Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....
virtualization
Storage Virtualization
Storage virtualization or storage virtualisation is a concept and term used within computer science. Specifically, storage systems may use virtualization concepts as a tool to enable better functionality and more advanced features within the storage system.Broadly speaking, a 'storage system' is...
technology used typically for backup and recovery purposes. A VTL presents a storage component (usually hard disk storage) as tape libraries
Tape library
In computer storage, a tape library, sometimes called a tape silo, tape robot or tape jukebox, is a storage device which contains one or more tape drives, a number of slots to hold tape cartridges, a barcode reader to identify tape cartridges and an automated method for loading tapes...
or tape drive
Tape drive
A tape drive is a data storage device that reads and performs digital recording, writes data on a magnetic tape. Magnetic tape data storage is typically used for offline, archival data storage. Tape media generally has a favorable unit cost and long archival stability.A tape drive provides...
s for use with existing backup software.
Virtualizing the disk storage as tape allows integration of VTLs with existing backup software
Backup software
Backup software are computer programs used to perform backup; they create supplementary exact copies of files, databases or entire computers. These programs may later use the supplementary copies to restore the original contents in the event of data loss....
and existing backup and recovery processes and policies. The benefits of such virtualization include storage consolidation and faster data restore processes.
Most current VTL solutions use PATA or SATA
Sata
Sata is a traditional dish from the Malaysian state of Terengganu, consisting of spiced fish meat wrapped in banana leaves and cooked on a grill.It is a type of Malaysian fish cake, or otak-otak...
disk array
Disk array
A disk array is a disk storage system which contains multiple disk drives. It is differentiated from a disk enclosure, in that an array has cache memory and advanced functionality, like RAID and virtualization.Components of a typical disk array include:...
s as 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, for disaster recovery
Disaster recovery
Disaster recovery is the process, policies and procedures related to preparing for recovery or continuation of technology infrastructure critical to an organization after a natural or human-induced disaster. Disaster recovery is a subset of business continuity...
purposes (scheme called disk-to-disk-to-tape, or D2D2T).
Alternatively, most contemporary backup software products introduced also direct usage of the file system
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...
storage (especially network-attached storage
Network-attached storage
Network-attached storage is file-level computer data storage connected to a computer network providing data access to heterogeneous clients. NAS not only operates as a file server, but is specialized for this task either by its hardware, software, or configuration of those elements...
, accessed through NFS and CIFS protocols over IP
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
networks) not requiring a tape library emulation at all. They also often offer a disk staging
Disk staging
Disk staging is using disks as an additional, temporary stage of backup process before finally storing backup to tape. Backups stay on disk typically for a day or a week, before being copied to tape in a background process and deleted afterwards....
feature: 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 an IBM Virtual Tape Server (VTS) introduced in 1997. It was targeted for a mainframeMainframe computer
Mainframes are powerful computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing.The term originally referred to the...
market, where many legacy applications tend to use a lot of very short tape volumes. It used ESCON
ESCON
ESCON is a data connection created by IBM, and is commonly used to connect their mainframe computers to peripheral devices such as disk storage and tape drives. ESCON is an optical fiber, half-duplex, serial interface. It originally operated at a rate of 10 Mbyte/s, which was later increased to...
interface, and acted as a disk cache for 3494 tape 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, while Luminex
Luminex Software, Inc.
Luminex Software, Inc. is a developer and provider of disk-based mainframe virtual tape products and technologies for backup, archive and disaster recovery.- History :Luminex was founded in 1994 by Brian Hawley, Michael Saunders and Arthur Tolsma....
has gained popularity and wide acceptance by teaming with Data Domain to provide the benefits of data deduplication
Data deduplication
In computing, data deduplication is a specialized data compression technique for eliminating coarse-grained redundant data. The technique is used to improve storage utilization and can also be applied to network data transfers to reduce the number of bytes that must be sent across a link...
behind 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 reduce Recovery Point Objective /RPO and Recovery Time Objective /RTO to approaching zero (or instantaneous).
Outside of mainframe
Mainframe computer
Mainframes are powerful computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing.The term originally referred to the...
environment, tape drives and libraries mostly featured SCSI
SCSI
Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...
. Likewise, VTLs were developed supporting popular SCSI transport protocols such as SPI (legacy systems), Fibre Channel
Fibre Channel
Fibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...
, and iSCSI
ISCSI
In computing, iSCSI , is an abbreviation of Internet Small Computer System Interface, an Internet Protocol -based storage networking standard for linking data storage facilities. By carrying SCSI commands over IP networks, iSCSI is used to facilitate data transfers over intranets and to manage...
.
The VTLs currently being adopted by Open Systems (including AS400 series) are dominated by FalconStor Software Inc.
FalconStor
FalconStor Software is a provider of disk-based data protection software. The Company's software includes Virtual Tape Library with data deduplication, Continuous Data Protector , File-interface Deduplication System and Network Storage Server , each enabled with WAN-optimized replication for...
The FalconStor VTL is the foundation of nearly half of the products sold in the VTL market, according to an Enterprise Strategy Group analyst.
See also
- BackupBackupIn information technology, a backup or the process of backing up is making copies of data which may be used to restore the original after a data loss event. The verb form is back up in two words, whereas the noun is backup....
- Tape libraryTape libraryIn computer storage, a tape library, sometimes called a tape silo, tape robot or tape jukebox, is a storage device which contains one or more tape drives, a number of slots to hold tape cartridges, a barcode reader to identify tape cartridges and an automated method for loading tapes...
- Disk stagingDisk stagingDisk staging is using disks as an additional, temporary stage of backup process before finally storing backup to tape. Backups stay on disk typically for a day or a week, before being copied to tape in a background process and deleted afterwards....
for an alternative approach - Emulation
- Storage virtualizationStorage VirtualizationStorage virtualization or storage virtualisation is a concept and term used within computer science. Specifically, storage systems may use virtualization concepts as a tool to enable better functionality and more advanced features within the storage system.Broadly speaking, a 'storage system' is...
- Linux Virtual Tape Library (Open Source)