In data storage, a tape library is a collection of magnetic tape cartridges and tape drives.
Tape libraries vary widely in cost and complexity. A typical library contains multiple tape drives for reading and writing data, access ports for entering and removing tapes, bar codes to track the tapes, and a device for mounting and dismounting tape cartridges. A library can include hundreds, or even thousands, of tapes.
What tape libraries are used for and how they work
Although tape drives have improved in features and reliability, the concept of writing data to magnetic tape has not changed for decades.
A tape library and its features must be compatible with the rest of an organization's data protection system, including the backup software. Tape library vendors provide compatibility lists of which backup software and hardware will work with their products.
In determining specifications for a tape library, an organization must typically figure out how big the library backup or archival set will be, including factoring in data growth.
Tape drives were the standard backup targets for decades. Though advances in technologies, such as large-capacity disk drives and the cloud, have made tape less fashionable as a backup device, it is still a popular choice for archiving. The Linear Tape File System (LTFS), for example, puts a file system on top of a tape library, improving its suitability for archive use cases.
Organizations of all sizes use tape libraries. A large enterprise will often use a tape library as a secondary backup target or an archive, if not as a primary backup means.
Benefits and drawbacks of tape libraries
A tape library's cost is generally less than disk or flash systems. Disk, for example, is expensive for archiving because of both upfront and operational costs.
Tape is also attractive for its durability and shelf life. In a disaster recovery situation, tape is a useful tool for retrieving data.
Encryption is offered for data security with tape libraries. In a common scenario, a backup media server, tape library, virtual tape library (VTL) or individual tape drive encrypts data as it is written. Encryption is especially important when tapes go off site because it protects the data in the event of a lost or stolen tape.
Tape libraries contain the capacity for massive amounts of information that is rarely accessed or changed. For example, one LTO-7 tape cartridge holds up to 6 terabytes (TB) of native capacity, or 15 TB compressed. With the explosion of data estimated to hit the level of multiple zettabytes by 2020, enterprises often turn to tape for long-term archiving. Retrieval of data from a large backup tape library can actually be faster than retrieving data from the cloud.
Though LTFS has improved filing systems and accessibility, a tape library can't match the access speeds of other technologies, such as disk. Because of the sequential nature of tapes, a user must roll through a tape to locate specific data.
Tape libraries can get complex, requiring management by the system's backup software. Support is also a concern. As technologies develop, an organization must ensure its tape library is compatible with all the other necessary components. For example, old tape drives may not work with a new library.
Tape library vs. tape drive vs. autoloader
Tape libraries and autoloaders automate backups and archives with multiple tapes. Tape libraries offer more capabilities than autoloaders, but are often far more expensive, as well as more complex because they have more tape drives.
A tape autoloader is a step up from a single tape drive for backup and archiving. Backup tape autoloaders provide automatic tape exchanges and more reliability than a stand-alone drive, but still have a limited capacity compared to tape libraries.
A tape autoloader typically consists of a tape drive, a tape magazine and a robotic arm that moves tapes between the drive and the magazine. The bigger tape library has multiple drives, and the robotic tape loader can access all of them, improving reliability. For example, if one tape drive in a library fails, the library could continue operation by using a different drive.
In hierarchical tape library storage management, the library removes rarely accessed files from network volumes and archives them to tapes. The library knows where files live through the use of barcodes. For retrieval, the robotic tape loader verifies that it is accessing the correct tape. Tape libraries are getting denser and, thanks to robotics, access speed continues to improve.
In the LTFS Library Edition, each cartridge's file system is logically presented with an overarching file system. The library's robotics mounts a given cartridge, which is transparent to users.
Tape library vs. virtual tape library and disk storage
A VTL is a hard disk drive-based storage system. It is designed to make disk storage look like a physical tape library to backup software. As with physical tape, data is written sequentially to a VTL, but can be written and read faster because it's on disk. Virtual tape libraries are frequently used for backup and archiving.
Because backup software historically didn't support the use of disk-based backup targets, VTLs enabled disk storage to be used for backup by posing as a tape library. Disk enables faster backup and recovery and more frequent backups.
VTLs and disk-to-disk backups are often packaged together with data deduplication. Both technologies will typically attach to a backup media server that manages them.
Tape library vendors, products and designs
StorageTek -- now part of Oracle -- is widely credited with inventing the first library to handle tapes more efficiently.
Recent enhancements from tape library vendors include the following:
- In 2011, IBM added LTFS support to tape libraries. IBM invented the LTFS technology, and was the first vendor to support it in libraries.
- In 2012, Oracle launched its first scalable tape library, the Oracle StorageTek SL150 Modular Tape Library, which enabled customers to start with an entry-level unit and expand it to 900 TB of compressed capacity.
- In 2014, Overland Storage launched the NEO XL-Series of automated tape libraries for scalable, high-density backup and archiving. Like other Overland tape library products, the NEO XL family enables partitioning a physical library into smaller libraries.
- In 2016, Quantum refreshed its Scalar LTO tape library family. The Scalar i3 and i6 support LTO-6 and LTO-7 tapes. The i3 is designed for small and medium-sized businesses, scaling up to 3 petabytes (PB). The i6 is for small enterprises, scaling up to 12 PB.
- In 2016, Spectra Logic announced upgrades to its TFinity tape library that, according to the vendor, make it the world's biggest tape library. The Exascale Edition can contain up to 53,460 LTO format tapes and 0.8 exabytes of compressed capacity.
Other tape library vendors include Dell EMC and Hewlett Packard Enterprise.
Recent high-profile uses of tape libraries include the following:
- In 2013, Nascar Productions chose Spectra Logic's TFinity tape library to store 180,000 hours of high-resolution video footage, including historical broadcast video and broadcast-related data sets.
- In 2016, NBC Olympics, a division of the NBC Sports Group, used Spectra tape library products -- the TFinity, T950 and T50e -- to provide video archiving and disaster recovery services for its production of the Olympic Games in Rio de Janeiro.