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5.7

Performance Analysis

In this section, we conduct an in depth performance evaluation of the NIC caching

scheme to examine various design issues. The performance of the exclusive and inclusive

caching schemes is analyzed based on experiments using the CSE, UCB and PSU work 

loads. Particularly, we focus on identifying the characteristics of the workload which

have significant impacts on performance. We also examine the impacts of bandwidth in

intra cluster communications, number of server nodes in the cluster, and update interval

of cache replacement on the performance of a cluster based web server.

5.7.1

The Exclusive NIC Caching Scheme

The exclusive NIC caching scheme uses the NIC memory as an extension to the

main memory cache in the main memory. The scheme aims at reducing the number

of disk accesses by increasing the cache hit ratio. As the NIC memory is used as an

extended cache in a cluster based Web server, the data items/files in the NIC cache can

be accessed by local and remote Web servers. However, when a Web server fetches data

from the NIC cache, it takes a longer latency time than fetching data from the main

memory cache. This is because the the connection between a Web server and a client is

through the TCP/IP (via the Ethernet NIC). Thus, the data has to be transferred from

the Intelligent NIC memory to the main memory, and then to the Ethernet NIC. On the

other hand, when data is accessed from the remote nodes in a cluster, the connection

between the nodes is through intelligent NICs. The access latency to the local NIC