I’m delighted to introduce a guest post today from Serve the Home’s Patrick Kennedy. I’ve been a big fan of the site since Patrick started writing about Windows Home Server last Summer – it’s a fabulous resource for self-builders, with in-depth posts on component selection, self-build home server projects and a whole lot more. Make sure you check it out.
A couple of weeks ago I invited Patrick to jump in on a debate that I know interests many of you; with advanced media streaming and transcoding capabilities, selecting the right processor for a server running Windows Home Server Vail is a matter of debate. Our recent Vail self-build project promoted a lot of discussion regarding the right processor to be used for Vail. Should you go with a low power processor like the Intel Atom, and if so, would you lose the ability to transcode high definition video on the fly? Or do you rip up the home server rule book and drop in a mighty Intel Core i7 that certainly has the power to transcode, but is expensive to run? Having built home servers with all manner of component combos, I asked Patrick if he’d be up for walking us through the debate.
Introduction
With the introduction of the VAIL Windows Home Server platform, based upon Windows 2008 Server R2, the platform will soon have modern underpinnings able to take advantage of newer hardware. The dilemma for the do-it-yourself WHS builder, given this modernization, becomes sticking to the tried and true ultra low-end x86 CPUs (the Intel Atoms of the world) or moving to a more modern CPU architecture such as Intel Nehalem variants. This article will provide a quick overview of the pros and cons of using the different routes both for the WHS V1 builder and for VAIL.
Silverlight-powered video streaming and transcoding in VAIL is perhaps the feature that will require the most CPU power. To be more precise, streaming only takes modest amounts of CPU power and most dual-core CPUs will be able to stream video smoothly. The feature that takes more CPU power is transcoding. As was explained by Ayca Akguc on Microsoft’s forums, the maximum Windows System Assessment (WinSAT) Tool CPU score needed for transcoding is approximately 6.6. From what I have seen over the past few months, processors such as Intel’s Xeon X3440, X3460, Core i7-920/ 930’s and AMD’s Phenom II X4’s all score higher than 6.6 and have no issues with transcoding 1080p source content in real time.
For current WHS systems, transcoding video is commonly done using a tool like Handbrake, DIVX, or Ripbot264 with the output video being stored on the media server. Although there is considerable debate on the usefulness of having Windows Home Server transcode and save video, I find that this solution works well to free up system resources on other machines. Having home server capable of heavy processing allows the use of a lower power CPU on their other PCs, or free up CPU cycles for other tasks. Needless to say, those not transcoding video will likely have little need for more than a very modest CPU in their Vail Home Server.
With that being said, here are some thoughts I have collected about current CPUs and the pros and cons of each in Windows Home Server, specifically in terms of features and the ability to transcode video when necessary.
Intel Atom
The Intel Atom line of CPUs has become a staple for low power Windows Home Servers. Many OEM builders use Atom CPUs in their WHS systems and Linux based storage solutions because they are fast enough to run Windows Home Server and to do XOR calculations for software raid (Linux).
After building at least fifty different WHS configurations over the past eighteen months, some of them based on Atom CPUs, I have a few recommendations for anyone pursuing this path. First, skip any non-64 bit enabled Atoms to maintain compatibility with VAIL. VAIL is a 64-bit platform, and when building a system there is little reason to use a 32-bit CPU. Second, skip the single core variants and get the Hyper-Threading enabled dual core CPUs such as the Atom N330 (if you can find one) and D510. Simply put, the cost differential is relatively low both in terms of initial purchase price and power consumption, and the benefit can be significant in terms of multiple process performance. This applies not only to user initiated tasks such as video transcoding, but also background tasks.
Intel does seem to be steering the Atom platform away from home server usage at the moment with the Pineview’s Atom D510 and NM10 chipset supporting only 2 SATA ports. Some manufacturers are adding JMicron 363 based chips to avert this limitation; however this still limits a user to four SATA hard drives on two controllers. Overall, for a small storage/ backup only system, the Atom still makes sense. For 2-4 drive systems, where the user does not plan to do CPU intensive tasks, an Atom-powered home server still provides the lowest power consumption available today. For users looking for larger storage capacities, and for more than just basic storage and backup capabilities, there are plenty of other options.
Intel Clarkdale CPUs
Intel’s Clarkdale CPUs are based upon a 32nm production process while the majority of 2010′s CPUs from AMD and Intel have been produced on an older and less power efficient 45nm process. Furthermore, the Clarkdale CPUs contain on-package GPUs which makes the CPU much more power efficient than the 73w max TDP rating would suggest. To the WHS user, the brief Clarkdale summary is very low idle power consumption, quite a bit of CPU power, and reasonable maximum platform power consumption.
In the Clarkdale series, my standard recommendation here is the Intel Core i3-530, despite the fact it does not have the features of the Clarkdale Core i5′s (such as the i5-650) that one may want like AES-NI acceleration, Turbo Boost and support for some virtualization functions (VT-d). What the Core i3-530 does represent is a low power dual-core CPU with Hyper-Threading that carries a street price of around $100 in late July 2010.
Performance wise, the Clarkdale CPUs are very strong. For WHS V1, background tasks can be accomplished while still transcoding video faster than a stock clocked but venerable Core 2 Quad Q6600. Moving up the range, the i5-650 enjoys approximately an 8-14% performance gain in video transcoding from what I have seen, but at a 50% price premium. For some users features like AES-NI acceleration and VT-d are going to be required and therefore justify the expenditure. Luckily, in terms of idle power consumption the Core i3-530 and i5-650 are very similar. The WinSAT CPU subscore for Clarkdale CPUs I have seen fall in the 5.8-6.3 range, so during tougher real-time transcodes, they may be slightly too slow (as noted above, 6.6 is apparently the maximum needed). Lower end CPUs fall on the lower end of this range, and many users cresting $200 on a CPU purchase for video transcoding will likely be better served by a Xeon X34xx series CPU.
From a power consumption perspective, idle power consumption (according to the unscientific Kill-A-Watt power meter) is very similar to the Atom dual core platforms. I have seen as low as 25w at idle recently on a platform based on the Intel BOXDH57JG mITX motherboard with the Core i3-530 which is within two watts of the comparable Atom D510 system. The difference is that under load the Clarkdale CPUs can consume 40 or more watts over the base idle power draw while the Atom CPU sees additional power draw in the single digit watt range. Although the 73w TDP of most Clarkdale chips is fairly high, realistically, it is a very difficult number to achieve because it requires stressing both the GPU and CPU simultaneously. Most Home Servers stress CPUs much more heavily than GPUs making the actual power consumption significantly lower than 73w in most cases.
Overall, the Clarkdale line provides very impressive idle power consumption and the ability to run the vast majority of workloads. I use the Core i3-530 in one of my Hyper-V testbeds because it provides a great mix of affordability, performance, and low power consumption.
Intel Xeon X34xxx Series CPUs
Intel’s Lynnfield based Xeon CPUs have one major home server feature that consumer CPUs like the Atom and Clarkdale lack, ECC support. Furthermore, Intel has been going to great lengths to integrate GPUs on package with both the Clarkdale and Atom designs. What this means, from a practical standpoint, is that the 95w max TDP of a Lynnfield based Xeon (non “s” low power models) is not directly comparable to the majority of the Clarkdale line-up (most have max TDP of 73w) and the Pineview Atoms with integrated GPUs because of the need for an extra GPU component on Xeon systems. Still, a Xeon 3400 platform and CPU with an onboard GPU and baseboard management functions will consume in the neighbourhood of 48w at idle, with only a SSD and no hard drives (for reference, the Core i3-530 in the same Supermicro X8SIL-F test bed using the onboard Matrox GPU instead of the on-package integrated GPU used 40w, 15w above what I have seen it do on other motherboards). That is considerably more than the Atom or Clarkdale systems but that is less than the max power consumption of four 7200rpm 3.5” disks as a point of reference.
