x86 servers with a single processor (as in single socket) are hardly unusual. They anchor the entry point for most vendors' product lines. Furthermore, beyond those systems that are sold specifically to be used as servers, an untold number of PCs sit under desks or in closets functioning as impromptu file or print servers.
However, pretty much since the advent of mass-market multiprocessing--in the Windows NT 3.51 era or thereabouts--uniprocessor servers have been very much the penny-pinching server option. Yes, they have fewer processors than their dual-socket brethren; that much is obvious. However, uniprocessor boxes have also typically jettisoned all manner of other capacity or reliability upgrades from memory to power.
This makes IBM's release of the uniprocessor IBM System x3350 notable and, perhaps, a harbinger of broader changes accompanying the wide adoption of multicore processors. (For whatever reason, this appears to have been a rather sub rosa announcement--rolled in almost incidentally with a broadened Lenovo partnership.)
For the x3350 is not another uniprocessor in the usual vein. The 1U rackmount server's features include:
- Hot-swap, redundant power supplies
- Integrated management controller
- Up to 8GB PC2-5300 DDR II 667MHz memory, using 4 DIMM slots
- Choice of dual- and quad-core Intel Xeon processors
- SAS or SATA drives, optionally hot-swap and RAID
In short, specs that wouldn't look out of place in a compact 1U dual-socket server.
Historically, each step down in processor count has tended to come with a concomitant cutting of other features--not just I/O or memory capacity (as might be expected), but also various and sundry management, reliability, and redundancy features. However, the storyline is getting more complicated.
On the one hand, server virtualization does appear to be pumping up interest in larger, scale-up servers. Part of the reason is that larger servers offer a degree of simplification through physical consolidation. They also tend to have the ultimate features to protect against memory failures and other hardware glitches. And server virtualization helps separate workloads and thereby makes effective use of this relatively expensive hardware.
At the same time, with quad-core well on its way to being the mainstream in x86 servers, individual processors look a lot like whole multiprocessor complexes of a few years back. This seems to be driving at least some interest in uniprocessor servers that aren't just cheap, cheap, cheap. Beyond x86 servers, Sun Microsystems' octal-core UltraSparc "Niagara" and "Niagara 2" servers are currently "uniprocessor" only (though with numerous cores and hardware support for multithreading, and multi-socket "Victoria Falls" versions coming). Of course, processors have been getting faster for pretty much forever, but the purchasing dynamics seem to be shifting with Moore's Law now reflected more by core count than by frequency.
The System x3350 doesn't foreshadow a massive change in how rackmount servers are designed and consumed. But it does offer an interesting data point that suggests the landscape is shifting.