Nowadays, more folks think of electronic vaulting as a substitute for an offsite tape approach. Many times, the possible data bandwidth between two sites is overlooked when estimating the backup window for tape copy/duplication.
Enterprise backup/restore software like TSM could make electronic vaulting possible through either a SAN or a high speed TCP/IP connection. However, devices that are currently available, such as McData directors or IBM DWDM, could extend a SAN to 103 kilometers. When the distance between two sites goes beyond this limit, storage-over-WAN is the only likely possibility. In this case, the data bandwidth would be a lot less than 100 Mbps and the backup replication of hundreds of GBs or TBs would take days instead of hours.
About the author: Giao Tran is currently a technical consultant at Sirius Computer Solutions, an IBM business partner. His technical areas are in IBM pSeries (RS/6000s), HACMP, SAN/NAS and TSM. You can reach him via e-mail at
This was first published in April 2002