Storage Basics: Deciphering SESAs (Strange, Esoteric Storage Acronyms), Part 2 Page 3 -

Storage Basics: Deciphering SESAs (Strange, Esoteric Storage Acronyms), Part 2 Page 3

Virtual Interface (VI)

The next acronym up for review is the Virtual Interface (VI). VI was originally designed by industry heavyweights such as Intel, Microsoft, and Compaq as a standard for interconnecting computer clusters. As such, VI was designed to provide a common interface for clustering software regardless of the underlying networking technology. In addition, VI is designed to help eliminate the overhead caused by network communication.

The VI standard specifies a combination of hardware, firmware, and operating system driver interaction to increase the overall efficiency of network communication. In application, VI provides two key functions: reducing CPU load and reducing latency. To do this, VI allows for direct memory-to-memory data transfer.

Memory-to-memory transfer enables data transfers directly between buffers and ignores normal protocol processing. VI also allows for direct application access, which enables application processes to queue data transfer operations directly to VI-compliant network interfaces without using the operating system.

Direct Access File System (DAFS)

Fitting right in the discussion of VI is the Direct Access File System (DAFS). DAFS is a protocol that uses VI capabilities to provide memory-to-memory data transactions for clustered application servers. Using the VI architecture and memory-to-memory data transfers, DAFS avoids the traffic overhead generated by operating systems.

As a little background, TCP/IP can be quite taxing on system resources, as it requires significant CPU processing while data packets are moved through the TCP/IP protocol stack. DAFS does not require this high overhead and can move the same data packets without all of the CPU overhead.

It does this by bypassing the protocol stacks and the operating systems to directly place data on the network link. Data is moved from the application buffers directly to the VI-capable NIC. In the process, overall network utilization is reduced and application throughput is increased. This flow of data takes a significant load off of the processor.

In the past two Storage Basics articles we have taken a quick look at some of the acronyms prevalent in the storage industry today. Of course, we’ve only just scratched the surface, as there are plenty more out there, and new ones are seemingly popping up a daily basis. As these first two articles have been a response to email queries, we look forward to more emails from you and the opportunity to unravel the mysteries of more acronyms in future SESA articles.

» See All Articles by Columnist Mike Harwood

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