Page 8 of 12 Why Choose Native Fibre Channel Backup? July 2001 Native vs. non-native Fibre Channel The importance of native Fibre Channel for effective SAN backup cannot be overemphasized.  The benefits discussed in this paper rely on backup devices being connected directly to the SAN. When Fibre Channel SANs first came into being, an effort was made to enable tape drive and library owners to connect their SCSI-based backup devices to the SAN.  This led to the development of SCSI-to-Fibre Channel routers that translate device mapping and addressing protocols between the two interfaces. SCSI-to-Fibre Channel routers were useful in early SAN implementations because they allowed users to experience many of the benefits of SANs without having to scrap expensive backup equipment.  However, these routers have a number of drawbacks that make them less than ideal for effective backup in mature SAN environments: Routers cause performance bottlenecks.  When multiple tape drives in a library are connected to the SAN through a router, all of the data to and from the drives passes through just one or a few Fibre Channel connections.  Forcing what should be multiple data streams into a fewer than optimum number of channels makes it difficult to use the full streaming capability of each tape drive. Routers introduce potential failure points.  When a library and its tape drives are connected to the SAN through a router, failure of the router takes the entire library and its drives out of service, even when they are functioning perfectly. Routers are difficult to configure.  An administrator must work with complex address mappings to assign multiple SCSI IDs to a single Fibre Channel connection.  In addition, the router must be reconfigured each time a new device is added. Routers aren’t scalable.  A lIbrary’s capacity can be expanded by adding tape drives, but if the router’s total bandwidth is already in use, the router must be replaced to accommodate the additional drives. Routers are expensive.  Routers can cost well over $10,000. As SAN administrators routinely upgrade their backup systems, they are turning to native Fibre Channel systems that eliminate the need for routers. Without the router, library and tape drive performance is used more effectively because data no longer has to pass through a fewer than optimum number of Fibre Channel connections.   When connected through a hub, multiple drives in a Fibre Channel library can be kept streaming (up to the hub’s data rate limit).  When connected through a switch, all of the drives in a library can easily be kept streaming. With a library connected directly to the SAN, the potential failure point at the router is eliminated.  Failure of this single piece of equipment can no longer take out the entire library. SCSI-to-Fibre Channel routers are less than ideal for effective backup in mature SAN environments. p1   p2   p3   p4   p5   p6   p7   p8   p9   p10   p11   p12