Apple’s Xserve G5 is a powerful machine -- just not in ways that are easy to get across to the IT market.
It is not a general-purpose computing barn burner. In business-style integer and floating-point tests, a 2GHz Xserve G5 comes in at about half the calculating power of a 2.2GHz Opteron running in pure 64-bit mode.
The G5’s memory performance is excellent, but it degrades in a linear fashion under load, whereas Opteron’s memory performance degrades more slowly (see “64 Bits on a Budget,” page 43). Opteron is cheaper, faster in common computation, and more consistent in terms of how fast it accesses memory.
In light of these facts, it’s hard to make a traditional IT case for Xserve G5. IT departments generally base their PC server purchasing decisions on criteria that reflect the strengths of the x86 architecture: the highest clock speed, the largest CPU cache, and the maximum amount of memory they can afford. With Xeon and Opteron, a system is the same thing as a computer. If that’s your viewpoint, nothing about Xserve G5 quickens your heartbeat.
The excitement Xserve G5 is generating within IT -- and there is likely more adoption than you think -- comes from integrating HPC (high-performance computing) principles into next-generation business applications. HPC is a flexible model that considers servers to be components of a logical system rather than systems unto themselves. Truly useful dynamic applications need this freedom to reconfigure their environment -- the logical system -- while they’re running.
Businesses want their infrastructures to adapt instantly to changes in resource loads and application mixes. Major vendors are offering solutions that add a dynamic element to enterprises, often involving an adaptation of grid computing.
Instead, Apple has crafted a plug-and-play HPC node that’s just as practical in pairs as it is in dozens. Apple invented proprietary system and I/O controller chips for the Xserve G5, with the specific aim of moving data in and out of the box and routing it around the CPUs as fast as affordable technology allows. This emphasis on throughput is smart engineering, but CPU performance remains an issue that Apple and IBM must address so that more traditional buyers can check it off their lists.
What’s next? Apple just announced a new Power Mac G5 desktop with dual 2.5GHz CPUs, a bus bandwidth of 1.25GHz (up from 1GHz), and liquid cooling. That’s a dramatic boost to computing speed, throughput, and constant load capacity, and the next Xserve G5 will undoubtedly share or exceed those specs.