Toward scalable Web systems on multicore clusters: making use of virtual machines
The Journal of Supercomputing
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Linux Virtual Server (LVS) is an open source technology which can be used to construct a scalable and highly available server using a collection of real servers. LVS load balances a variety of network services among multiple machines by manipulating packets as they are processed by the Linux TCP/IP stack. One of the most common roles for LVS is to act as a front end to a farm of web servers.This paper documents a series of experiments performed on LVS by Mission Critical Linux, Inc. in a cooperative effort with Intel Corporation. The objective of these experiments was to evaluate LVS's ability to distribute web requests among several servers. We investigated a variety of LVS configurations and offer a comparison of LVS's ability to scale on Linux 2.2 versus Linux 2.4. In contrast to similar evaluations, our entire test effort was accomplished using open source software on Linux based platforms.Our results show that in a uni-processor environment the performance of LVS on Linux 2.4 is on par with Linux 2.2, however in a multi-processor configuration, Linux 2.4 significantly surpasses Linux 2.2. LVS on Linux 2.2 actually exhibits minimal scaling in a multi-processor environment. We reveal the detrimental impact that multiple devices sharing interrupts can have on LVS throughput. A comparison of LVS to a commercial load balancer indicates that LVS is a viable alternative to the more expensive, proprietary solution. Our results show that LVS is nearly twice as cost effective in terms of price/performance when compared to the hardware based load balancer. Lastly, we document the steps necessary to enhance the capabilities of our load generator which in turn reduces the amount of client hardware needed.