Again in the second experiment, an increasing number of clients continuously made CGI requests to either of two Web sites hosted at node S. However, these requests are I/O-intensive, consisting of reading a 100 MB file and returning a 10 KB reply. Because requests and replies are small and each request involves considerable disk I/O but little processing, the bottleneck resource is the disk. We reserved 50% of S's disk bandwidth to the Web site of interest and measured the latter's average throughput over three minutes. YFQ's sort queue was configured with a batch size of 4 requests. During the measurements, the site of interest had ten clients and the competing site had a varying number of clients. Figure 6 shows that in the absence of other load, Eclipse/BSD gives to the site of interest essentially all of the bottleneck resource, even though the site has only 50% reserved. When the load on the competing site increases, the throughput of the site of interest decreases. However, on Eclipse/BSD, the throughput bottoms out at roughly the reserved amount, whereas on FreeBSD the throughput decreases without bound. This shows that FreeBSD and Eclipse/BSD are equally good when there is excess disk bandwidth, but when bandwidth is scarce, Eclipse/BSD is also able to guarantee a minimum disk bandwidth allocation.
