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VTLs are built around four different architectures that, in various ways, address these questions.
- VTL storage appliance. The VTL is a single appliance that contains both the disk drives and the controllers that host the VTL software. Examples include units from Copan Systems Inc., EMC Corp., Quantum Corp. and Network Appliance (NetApp) Inc.
- VTL server appliance. A dedicated server is loaded with VTL software and connected to external disk arrays over Fibre Channel (FC). Diligent Technologies Corp., FalconStor Software Inc., Maxxan Systems Inc., Neartek Inc. and Sun Microsystems Inc. each provide this type of technology.
- Grid-based architecture. The S2100-ES2 from Sepaton Inc. allows users to add server nodes to their VTLs and scale to meet the capacity demand for either more performance or additional FC ports.
- Tape library based. ADIC's Pathlight VX series and Spectra Logic Corp.'s Spectra T950 allow users to store data to tape or disk media within their tape libraries.
|Enterprise virtual tape libraries|
|Click here for a comprehensive list of Enterprise virtual tape libraries (PDF).|
Each architecture has its pros and cons. VTL storage appliances are easy to set up and deploy; but when performance or capacity limits are reached, users need to deploy more VTL storage appliances, thereby introducing management headaches. VTL server appliances may allow users to scale to larger capacity and performance thresholds and use different vendors' storage, but may become performance bottlenecks or introduce untested configurations. Sepaton's S2100-ES2 grid-based approach scales economically when capacity, connectivity or performance thresholds are reached, but is eventually subject to the same limitations as storage appliances. ADIC's Pathlight VX series and Spectra Logic's Spectra T950 manage disk and tape in a single frame, but create a dependency on the VTL to manage tapes created and exported from the VTL.
This was first published in August 2006