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.

Free IT resource Virtualization Insights from Top Experts - Learn how virtualization gets real! Sponsored by Dell Free IT resource Try Sun servers, workstations and storage products free for 60-days. Sponsored by Sun Microsystems DOWNLOAD REPORT Looking for this InfoWorld Special Report in one complete, printable format? Download it for free. >> Special Report: Linux fit for the server room

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.

Click for larger view.

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.

Finally, regarding the four systems tested, all proved to be solid machines. Among the Opteron units — all 1U boxes — the Appro and Pogo Linux systems offer great value and horsepower for the price, while the Newisys offers a more substantial feature set, including a management card and hot-swap SCSI drives. The Itanium-based HP system, a 2U box, offers great expandability and redundant everything, albeit at a higher price.

Three Little Opterons

The Opteron has one advantage over the Itanium: It can run 32-bit applications in native mode, while the Itanium runs 32-bit applications in emulation mode. This means legacy 32-bit applications will run slower on the Itanium than on Xeon systems or Opteron. It also means that applications can be ported to Opteron gradually, weaving in 64-bit support component by component, without requiring a wholesale rewrite before deployment.

Each of the three Opterons I tested ran SuSE Linux’s Enterprise Server, while the Itanium system from HP ran Red Hat’s Enterprise Linux AS. All four systems came with Apache installed; I also installed Zeus Web Server 4.2r2, which is optimized for both Opteron and Itanium.

The Appro 1122H is a value-oriented 1U server, available with two 1.6GHz or 1.8GHz Opteron processors, up to 16GB of RAM, one or two ATA or SCSI drives, and two 10/100/1000 Ethernet interfaces. My test unit came with two 1.6GHz processors, 2GB of RAM, one 80GB ATA hard drive, and SuSE Linux Enterprise Server already installed.