64-bit Linux: Ready for prime time?

With the arrival of the AMD Opteron and Intel Itanium, commodity servers built on these processors have joined proprietary RISC systems from IBM, Sun Microsystems, Hewlett-Packard, and others in the 64-bit landscape. With prices starting at just over $2,000, Opteron and Itanium systems — running Linux or Windows — are already carving out a niche in high-performance computing clusters, where they are used to run compute-intensive scientific- and financial-modeling applications. Eventually they will replace their 32-bit forebears in corporate datacenters, and clusters of them may even challenge 64-bit Unix systems costing hundreds of thousands of dollars.

How long this will take depends on software vendors, who must rewrite their applications for the new 64-bit CPUs. Many operating systems are already available for Opteron and Itanium. In addition to Red Hat Enterprise Linux AS 2.1, which supports Itanium, and SuSE Linux Enterprise Server, which supports both Itanium and Opteron, there is an Itanium version of Windows Server 2003, and Itanium and Opteron versions of Turbolinux Enterprise Server 8. Databases such as IBM DB2 and Oracle 9i, and application servers from IBM, Oracle, and BEA Systems should begin to be available this year. But enterprise app vendors, with the exception of SAP, have been slow to commit to a road map of support.

Ultimately, the appeal to business software vendors and customers alike will depend on performance. Compared to the previous generation of 32-bit systems based on AMD’s Athlon MP and Intel’s Xeon MP, the Opteron and Itanium CPUs support much more memory per processor, higher-speed connections between memory and the CPU, and faster interprocessor communications. To what extent do these advantages translate into real performance gains? To find out, I looked at Web server performance on four 64-bit Linux systems, including an Itanium 2 server from HP and Opteron systems from Appro, Newisys (a company partly funded by AMD), and Pogo Linux.

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There are many other types of benchmarks that could have been used here, but all are subject to various problems, including finding code that will run on both Itanium and Opteron processors; that is optimized for 64-bit operation; and that is not associated with some major player. Because system and database benchmarks are typically oriented to a specific type of hardware or operating system, I compared the systems based on Web server performance, using the industry-standard Apache Web server, which was included as part of the standard release of Linux on all four systems, as well as Zeus Technologies’ Zeus Web Server.

Load testing these Web servers on the four systems produced interesting results. First, Web-server performance on these systems was substantially better than on the 32-bit Xeon hardware I compared them against, suggesting that IT shops would benefit from migrating their Web server farms to 64-bit systems today. Second, Apache performance on Itanium was abysmal compared to Zeus performance; if you’re considering Itanium for Web serving, go with the Zeus Web server. Third, the performance differences between Apache and Zeus on Itanium point to the need for software that not only runs on 64-bit hardware, but is optimized for it.