08-16-2017, 10:19 PM
INTRODUCTION
Network bandwidths have been increasing and Latencies through these networks have been decreasing. Unfortunately, applications have not been able to take full advantage of these performance improvements due to the many layers of user level and kernel level software that is required to get to the network. The Direct Access File System (or simply DAFS) developed by Microsoft, Compaq and Intel, significantly reduces the software overhead between a high performance CPU/memory subsystem, and a high performance network. Direct Access File System promises to improve performance for distributed applications, especially clustered and tiered database applications. At its heart is the concept of a userlevel interface directly to the network hardware that bypasses traditional operating system mechanisms: I.E. the virtual interface. The design focus of the Direct Access File System is to achieve low latency, high bandwidth communication/data exchange between processes running on two nodes within a computing cluster, with minimal CPU usage. Low latency and sustained high bandwidth are achieved by allowing a user process direct access to the network interface, avoiding intermediate copies of data and bypassing the operating system in a protected fashion. CPU utilization is minimized by avoiding interrupts and context switches whenever possible.
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