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What the Heck Is HyperSCSI?

Data transport protocol iSCSI may have begun gaining industry recognition as a low-cost alternative to Fibre Channel in storage networks -- if not exactly traction just yet -- but its not the only candidate sitting in the hallway (see Microsoft Sparks iSCSI Liftoff and iSCSI Gets Go-Ahead). Another transport protocol, HyperSCSI, is also angling for the position of providing inexpensive, Ethernet-based SANs to the masses.

The HyperSCSI protocol, originally developed by researchers at Singapore's Data Storage Institute (DSI) in 2000, is designed for transmitting Small Computer System Interface (SCSI) data and commands across raw Ethernet, allowing companies to connect to and use remote SCSI and SCSI-based devices over a network as if it were directly attached locally. The DSI is a joint venture of Singapore's Agency for Science, Technology, and Research (A*STAR) and the National University of Singapore (NUS).

By contrast, iSCSI -- developed under the auspices of the Internet Engineering Task Force (IETF) -- sends SCSI commands over TCP/IP.

HyperSCSI's supporters claim that it not only dramatically slashes the price of SAN connectivity compared with both Fibre Channel and iSCSI, but also that it offers far better performance than its IP-based cousin.

By sending data blocks across raw Ethernet, the protocol completely eliminates the TCP/IP overhead that slows down iSCSI, according to HyperSCSI's supporters. In fact, the protocol's developers claim, it can match Fibre Channel performance with only a 21 percent increase in CPU utilization and 3.4 times more IRQs (Interrupt Requests, which are used to signal to a CPU that a peripheral event has started or terminated). Meanwhile, they claim that iSCSI chews up 33 percent more CPU utilization and 6 times more IRQs to match Fibre Channel's performance.

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