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Interoperability with your hardware and software is one of the most important selling points of virtual tape products. Virtual tape products differ significantly in the breadth of interoperability support they deliver. Interoperability must be measured along several dimensions. The first and most obvious dimension refers to the number of tape formats and libraries a VTL product supports. To minimize the disruption associated with introducing disk-based technologies into the environment, users should look for virtual tape products that can present disk resources identical to their existing tape libraries and tape formats to the backup hosts; the broader the VTL device's support, the greater the operational efficiencies and investment protection. Storage managers should seek out a VTL product that emulates all of their existing devices, as well as any new platforms being considered for acquisition in the future.
|Hardware Virtual Tape Libraries|
|Click here for a comprehensive list of hardware virtual tape libraries (PDF).|
Most enterprises have many heterogeneous hosts consisting of a variety of open-systems flavors and, often, a mixture of open systems and mainframe. Hosts will vary in their connectivity, with mainframes supporting ESCON and FICON, and open systems relying on a combination of Fibre Channel and SCSI. Make sure the VTL supports a variety of heterogeneous hosts and connectivity options, and find out if the VTL will support next-generation SATA disk platforms. The VTL should also support heterogeneous platforms concurrently. Some vendors claim to support heterogeneous platforms, but require the separation of the disparate hosts onto different virtual tape units. This leads to independent data-protection silos that limit the economies of scale and operational leverage in the storage environment. Neartek supports a combination of mainframe and open-systems hosts within a single product. Diligent provides mainframe and open-systems support, but with distinct products. All other VTL vendors are focused on the open-systems market.
Media lifecycle automation
Along with differences in product architecture and interoperability support, virtual tape products vary significantly in their media lifecycle automation capabilities, particularly in the way they handle offsite media management and vaulting. Vendors have developed a number of alternative approaches to managing tape as part of a virtual tape solution. Understanding this aspect of a particular virtual tape product is absolutely critical.
This was first published in November 2005