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Traveling data during backup

In a SAN environment where you have a server, centralized disk and tape, how does data travel during backup of a server with data residing on the centralized disk? For example, once backup server initiates backup of a server, does data go from disk to switch then to tape OR data goes from disk to switch to server and back to switch then to tape? I hope that wasn't confusing.

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Not confusing at all. Don't think of the switch as being an active part of the data path. Think of it as a piece of wire. The data path goes through the storage wiring into the server and from there back through the wiring onto tape.

Serverless backup has the concept of data movers that make disk to tape transfers that do not travel through the server. However, serverless backup is still pretty much a fairy tale and requires a great deal of synchronization between host file systems and the backup system - including the data mover. The data mover can reside almost anywhere - including a switch. Someday...

Marc Farley

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This was first published in October 2001

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