Dell's virtualisation servers surge ahead

Virtualisation servers are systems designed to deliver more of the capacity that virtualisation hosts need to run optimally. Virtual machines, or VMs, crave lots of RAM and dedicated CPU resources. Both PowerEdge R805 and R905 servers are highly scalable in terms of RAM, which is often the gating factor on the number of VMs that can be run simultaneously on a server. The entry-level R805 model can accommodate 128GB across 16 slots, while the enterprise-oriented R905 has 32 SIMM slots that hold 256GB, when using 8GB DIMMs. These memory sticks are now fairly easy to find, albeit at elevated prices. The baseline RAM for these systems is 667MHz DDR-2, which is slower than other Opteron-based servers in this category.

The second criterion for good performance is access to the CPU. On these servers, the processing power is delivered by either quad-core or hexacore AMD Opteron processors. The R805 server I tested came with two 2.6GHz hexacore Opteron 2435 processors, while the R905 came with four 2.6GHz hexacore 8435 chips. The Opteron processors were the first x86 processors to come to market with six cores each. Intel is expected to ship a hexacore processor in 2010.

With a total of 12 threads on the R805 and 24 on the R905, Dell's servers provide plenty of processing power. Only a severely overloaded server is likely to exhaust the processing capabilities of these chips. And it would be more likely that such a server would run into RAM constraints before maxing out these CPUs.

A final requirement of virtualisation servers is plenty of bandwidth. These systems are not intended to provide the primary storage for the VMs, nor for their workload. As a result, the servers tend not to support large numbers of high-capacity disks on-system. Rather, they depend on accessing both VMs and data via the network. Because of this design, which is increasingly common in servers of all types, virtualisation servers typically have numerous large pipes. The R805 and R905 both have four slots stocked with 1GbE cards that support TCP/IP offloading (TOE). Two of the four slots can hold 10GbE network adapters.

One obvious requirement of all virtualisation servers is the ability to boot an operating system that runs a hypervisor. Both Dell systems enable users to boot at least two different operating systems. There is the OS on the hard drives, which in the case of this review was Microsoft Windows Server 2008 running the Hyper V hypervisor. And there is a second optical drive that plugs into the internal USB port.

There are three standout results in the benchmarks of these systems when compared with last year's models. All have improved in conspicuous ways, especially with respect to performance and power consumption. The R805 is also significantly more affordable than last year's model.

Power consumption has also dropped dramatically. Last year, the R905 sucked up a full 652W to run at 100 percent capacity. This year, it required 405W, a 38 percent drop. The R805 went from 411W to 260W when running at 100 percent. This is an excellent result. Two years ago, an average workstation running at full tilt could easily surpass this level of power consumption.

Both systems impressed us with their capabilities and, especially, by how much they've progressed in the year since our last review. We rate both systems as excellent for performance and power usage. Expandability is good on both systems, but not out of the ordinary for servers in this category. The nod goes to the R905 for its greater headroom. Serviceability is identical to last year, as these machines are essentially the same except for processor upgrades and minor hardware tweaks. As to value, the R805's enormous price drop propels it ahead of the R905.