InfoWorld review: Dell’s virtualization servers surge ahead

Oh, what a difference a year makes! In October of last year, I reviewed a pair of virtualization servers from Dell. Specifically, I examined the PowerEdge R805 and R905 models, which defined the new category of servers purpose-built to support virtualization. At that time, HP did not offer virtualization servers, but with the obvious embrace for the technology by IT departments everywhere, HP has finally entered the fray, trying to beat back Dell and fend off challengers such as Lenovo. I’ll look at how those vendors stack up against each other in a head-to-head shoot-out in an upcoming review. In this review, I look at the updates to the Dell servers I examined last year.

Whereas last year’s servers were powered with quad-core AMD Opterons, today’s systems are driven by the new six-core or “hexacore” Opterons, code-named Istanbul. (Readers who remember their Latin will note that the six-core chips do not follow the tradition of using Latin prefixes for core count that was established with “quad-core.” This is presumably because the term “sexacore” was a tad edgy for vendors’ marketing and legal departments — hence, hexacore.) Because these processors are pin-compatible with the quad-core Opteron forebears, Dell was able to upgrade the systems without rolling out a new model. As a result, the company stuck with the original model numbers and the original positioning of these two machines.

[ Intel’s newest server processors bring big iron horsepower to small offices. See the InfoWorld Test Center review: “Nehalem tower servers: Dell, Fujitsu, HP square off.” ]

In our tests, we find that the performance has greatly improved. Further, the price of the R805 has come down significantly. As a result, the price-performance ratio, always a strength of Dell’s product lines, is hugely better than it was a year ago. In addition, power consumption is vastly improved for both models. It’s hard to recall so much progress made in three different areas in any year-over-year hardware comparisons.

Many servers in one

Virtualization servers are systems designed to deliver more of the capacity that virtualization hosts need to run optimally. Virtual machines, or VMs, crave lots of RAM and dedicated CPU resources. Both these 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.

[ If you can’t view the tables in this article, read the original story at InfoWorld.com. ]

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.

In their six cores, the Opterons offer exactly six threads of execution. Today’s Nehalem Xeon processors from Intel come with four cores, each of which can run two threads of execution simultaneously, using Hyper-Threading. Consequently, a quad-core Intel Xeon offers more threads per chip. However, two Intel threads share a single 256KB L2 cache, while the cores on the AMD Opteron are given a full 512KB of L2 cache each. How much of a difference this cache makes depends entirely on the workload. Light workloads that do not require large amounts of data in RAM to complete transactions will work well on Nehalem servers with Hyper-Threading enabled. Database applications and enterprise workloads will prefer the greater cache of AMD Opterons. (The Nehalem chip’s Hyper-Threading can be disabled to reduce — but not eliminate — the cache limitations; however, this step limits the chip to a total of four threads.)

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 virtualization 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, virtualization 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 virtualization 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. At boot time, it’s possible to set the machine to boot from this drive rather than the hard drives. Consequently, with both systems, you can run different hypervisors without having to configure the software or the hardware. For many sites, this is not an important advantage, as most IT organizations choose one hypervisor as the standard and build their infrastructure around that choice. However, sites with multiple hypervisors in use will be able to move these servers back and forth between hardware pools without having to reconfigure them.

Test results and report cards

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.

Comparing performance of virtualization servers is best done using VMmark, which is freely available from VMware. However, this is a complex test suite that is both hard to configure and difficult to run. Because of this, all results, including ours, come from the vendors themselves. The R905 achieved 27.5 tiles (the unit of measure in VMmark). Last year, the same model weighed in at 14.8 tiles. This is a stunning improvement of 85 percent year over year. The R805 promises similar gains. Dell has not yet published certifiable VMmark results for this machine, but expects a result between 15 and 16 tiles. Similarly configured servers from HP fall within this range, so it’s safe to project a midpoint of 15.5 tiles. This number marks a 96 percent improvement over last year’s R805 score. This system is faster than last year’s R905 model, which had twice the number of processors. It’s not often that one year brings a near doubling of performance based primarily on processor upgrades — kudos to AMD.

Power consumption has 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.

Finally, the pricing: The R905 has dropped only about 5 percent, from $19,812 to $18,906. The R805, however, has dropped very significantly; at $7,643, it’s nearly half of last year’s price. Given its performance and scalability, the R805 is a standout in price-performance and should be attractive to SMBs and small enterprises.

Both systems impressed me with their capabilities and, especially, by how much they’ve progressed in the year since our last review. I 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.

The upshot is that, using the weightings favored by InfoWorld, these systems are essentially tied. If your organization values characteristics differently, you should recalculate the scores. Either way, you’re likely to find that these servers are closely matched in terms of deliverables. I find myself attracted to the R805 and the prospect of doubling up on it in lieu of buying a single R905. This strategy has a lower overall price point and offers sites finer granularity in their virtualization infrastructure, while not consuming extra rack space. Each additional system at an IT site, however, does have associated costs beyond the hardware and bundled software, so each group needs to evaluate this approach in the context of its own preferences.

This story, “InfoWorld review: Dell’s virtualization servers surge ahead,” was originally published at InfoWorld.com. Follow the latest developments in hardware at InfoWorld.com.