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libraries are also known as virtual tape systems (VTS), disk-based libraries (DLs) and disk-based backup devices among other market names. Virtual tape technology is not as "flashy" as intelligent switches and storage virtualization software. However, virtual tape is a time-tested, proven technique with revenue-producing products that provide virtualization via abstraction and emulation of specific storage resources.
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When placed offsite, VTLs can help to reduce or eliminate manual tape handling and the possibility of data theft or loss. By having a VTL located offsite, recovery and restore operations can be expedited while multi-site clustered environments can continue to operate in a failover mode maintaining secondary data protection capabilities.
Knowing what your requirements are enables you to make an informed decision on the applicable type of technology. For example, if you need to support both open systems and IBM mainframe tape processing from a single VTL, your options may be more limited than if you were looking at just open systems support. While VTLs enable disk-based backup and data retention, a key capability and differentiator is the ability to emulate various tape drives and libraries. This emulation capability enables coexistence with existing backup software and procedures.
From an operational standpoint, VTLs that support BC and DR should provide emulation of various tape drives and libraries to coexist with existing data protection software. By providing emulation, a VTL with remote copy capability can support remote vaulting to facilitate BC and DR. VTLs can also help support consolidation of IT resources, including multiple smaller tape drives, libraries and stackers into a central automated data protection device.
To improve on reliability, availability and serviceability (RAS) look for VTL products with redundant components that can be leveraged for proactive and transparent failover to isolate and contain faults. Some VTLs leverage a redundant, peer or clustered approach where front-end controller nodes can failover to other nodes with back-end storage being transparent. Clustered VTLs provide the ability to scale availability, connectivity, performance and capacity.
Many VTLs leverage detached or modular storage and, in some cases, can utilize existing SAN-based storage systems. VTLs with redundant controllers should be able to present a target emulated tape device to a host system to simplify server and backup software administration. Minimum RAS features to look for include dual or redundant controllers, power and cooling; hot swappable components, data protection and integrity safeguards; and RAID protected back-end disk storage.
VTL technologies can be a powerful and integral piece of an overall data protection strategy and provide support for DR and BC specifically. In addition, VTLs can provide an abstraction layer to help you transition from your current data protection strategy to a new strategy while leveraging existing staff skill-sets and procedures.
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About disk-based backup for SAN and NAS?
About the author: Greg Schulz is founder and senior analyst with the IT infrastructure analyst and consulting firm StorageIO. Greg is also the author and illustrator of "Resilient Storage Networks" (Elsevier) and has contributed material to Storage Magazine and other TechTarget venues.
This was first published in February 2006
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