By Tom Yager InfoWorld | on June 08, 2009
Pros: Ready to run. True headless booting. Unlimited licenses for Windows, Mac, and NFS file sharing clients. 12 1,066MHz DDR3 DIMM sockets leverage Nehalem's triple-channel on-chip RAM controller. Independent system management controller ('lights out management') with GUI, SNMP, and IPMI 2.0 support. Optional integrated hardware RAID controller with battery-backed RAM cache.
Cons: Lights-out management controller lacks KVM over IP support; no official serial over LAN support. Proprietary drive trays are not user-upgradeable with raw drives.
With only 8GB of RAM to Nehalem Xserve's 24GB, the older server was underconfigured by modern standards, a fact that may have contributed to its poor showing despite the fact that the machine did not resort to paging processes out of RAM during testing. Poor scalability under parallel memory-intensive loads was a characteristic of Intel x86 pre-Nehalem, symptomatic of a bus architecture that imposed a heavy penalty on memory access. That penalty is gone.
The smooth scalability of Nehalem Xserve under rising parallel load in the SPECjbb2005 tests not only highlights the Nehalem architecture's improvements, but also Mac OS X Leopard Server's exploitation of the architecture. The kernel's deft assignment of tasks to processor cores and thread units, and its mapping of physical memory to leverage NUMA (non-uniform memory architecture), keeps Nehalem Xserve's six memory channels working together. It took Microsoft several years to fix Windows Server to make appropriate use of AMD64 NUMA, the model Intel adapted for Nehalem. If early benchmarks are any indication, Apple seems to have gotten NUMA right on its first try.
The 2.26GHz Nehalem Xserve is probably the greenest server this side of UltraSPARC T2, and for many uses, it will outperform the eight-core, 3GHz model it replaces. Xserve meets Apple's exacting standards for environmentally responsible manufacturing -- it's so non-toxic that it's practically edible -- but in its maxed-out 2.93GHz, eight-core incarnation, Nehalem Xserve is more about high speed than low power. Mac OS X Leopard Server lacks the equivalent of Windows Server's energy profiles. There's no way to make the server less than it is for the sake of enhancing savings and quiet at times of low compute demand.
The new Xserve's power draw at idle is higher than that of the previous Xserve. That said, Xserve makes a greater effort than most rack servers to run as quietly as its workload permits. The fan array can get loud, but Xserve never emits the piercing high-frequency din that high-end 1U rack boxes can broadcast. Nehalem Xserve's noise is very effectively muffled by my GizMac XRackPro.
One power-saving option holds great appeal for shops that make heavy use of networked storage. Apple now sells a 128GB solid-state (flash) boot drive for Xserve. This can greatly reduce power consumption, heat, and noise, and with no seek or rotational latency, the system loads the kernel and apps lightning fast. This comes at the expense of write speed, though. With its plentiful cache, further abetted by the cache on the server's optional hardware RAID controller (highly recommended), a single 1TB Western Digital SATA drive was two to three times faster in write performance than the SSD. Look to the solid-state drive option to simplify and slim your Xserve, not to speed it up.