HP bests Sun in a dual-core server duel

See correction at end of review

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Dual-core technology is here. It's mainstream, and it's now part of the enterprise server ecosystem. IBM and Sun Microsystems led the charge with dual-core versions of their Power5 and UltraSparc processors; now AMD and Intel are offering dual-core versions of their 32- and 64-bit Opteron and Xeon processors.

The market leaders, of course, will be the x86-based chips. Here AMD has an advantage because its processor architecture allows the dual-core Opteron to be a plug-in replacement for its single-core predecessor. This allowed companies such as Hewlett-Packard and Sun to release dual-core upgrades of existing Opteron-based systems, such as the four-processor versions of the HP ProLiant DL585 and the Sun Fire V40z.

InfoWorld has already reviewed the single-core implementation of the ProLiant DL585 and the Sun Fire V20z, the 1U dual-processor sibling of the Sun Fire V40z. Both were solid performers, although the DL585 had the edge in manageability and high-availability features. In short, you'll find that the dual-core versions of these Opteron servers remain solid systems. Both companies have also made moderate updates to the server hardware since the previous reviews, but overall, the same conclusions hold: The ProLiant DL585 is a better server, with better management, I/O and high-availability monitoring features, and a better RAID controller, at a slightly better price.

If you don't need those extra features, however, the Sun Fire V40z offers more internal storage and a smaller form factor, for about 10 percent more in cost. (Prices were calculated by assuming an identical configuration -- four 2.2GHz dual-core processors, 16GB RAM, two 73GB hard drives, and no extra-price software or services.)

It's all about the processor

The key to both machines' success, and HP's and Sun's abilities to bring them to market quickly, is the architecture that AMD uses for its Opteron server-class microprocessors. A single-core Opteron processor die -- the actual silicon -- contains the processor core, which has the queues, execution units, and on-chip cache. However, it also contains an on-chip crossbar switch. Three things plug in to that switch: the core, an on-chip integrated memory controller, and the on-chip high-speed system bus, which AMD calls HyperTransport.

The dual-core design for the Opteron processor is almost identical to that of the single core, except that there are two cores, each of which plugs in to the crossbar switch. The two cores share the same memory controller and HyperTransport bus. This means that, first of all, the Opteron design is inherently scalable; you can easily imagine AMD being able to plug four, eight, or more cores in to that same architecture. But second, this design doesn't require additional physical circuitry on the server's main logic board or additional pins for the chip. Thus, AMD's dual-core processors are simple plug-in replacements for the single-core chips.

The only changes that were required, as far as I can tell, may have been to the system BIOS, in order for the firmware to understand that there would be more cores than physical processors. Also, because each core generates heat, a plug-in dual-core processor would need to run at a slower clock speed than the original single-core chip, if the goal is to keep current draw and generated heat the same. There are also minimal bottlenecks because the cores must share the same memory and HyperTransport buses.

The net result, according to benchmarks I've seen, is that switching from, say, a 2.6GHz single-core to a 2.2GHz dual-core Opteron processor speeds up things about 30 percent to 40 percent. Of course, that's a rough estimate because a lot depends on the application's CPU utilization, but the upshot is this: There's a significant performance boost to using dual-core chips.

Hewlett-Packard ProLiant DL585

The HP ProLiant DL585, which I reviewed in a 2.2GHz dual-core configuration, is stronger in high-availability and expandability features and has a more sophisticated onboard management processor that offers an intuitive graphical user interface. Windows users, in particular, will find that the DL585's management interface is more comfortable and user-friendly than the Sun V40z's command-line-based service processor and that it allows for continuous monitoring and alerting for system faults.