In an SOIP feature I suggested that, because UDP datagram delivery was unreliable, Zetera Z-SAN data delivery could be compromised. Not so. Here is a response, a correction, from Ryan Malone, Zetera's senior director of marketing:

"UDP does not concern itself with guaranteed data delivery, leaving that responsibility to the application that sits above the UDP port. Zetera's Z-SAN technology absolutely guarantees delivery of each and every transfer in an atomic fashion. There is an ACK response for every transfer."

"If that transfer is lost (due to a lack of an ACK), then the protocol will re-issue the command. If commands continue to have no ACK, then the file system reports the error. Because UDP leaves responsibility of guaranteed data delivery to the application above the UDP port, Zetera has more flexibility and control over exceptions than TCP allows. Zetera's Z-SAN technology was built on a UDP/IP foundation with reliability protection that puts its data delivery reliability on par with Fibre Channel.”

The original text in the SOIP feature has been amended to include this point. It's obvious that MIT wouldn't be concerning itself with a Z-SAN-based project unless data delivery was rock-solid.

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