21st Century Server Choices

Lots of people base their server form factor choice on what they are used to buying. Critical database applications equal a high-end server. Less critical applications: midrange server. High-end machines used to find a home at larger companies and cheaper servers would typically be attractive to SMEs. I am oversimplifying but those are the clichés that pop up when you speak of server choices.

Dividing the market into who should or should not buy high-end servers is so... 20th century. Server buying decisions today are a lot more flexible and exciting for those who keep an open mind. In the world of virtualization your servers are just resource pools of networking, storage and processing. Do you buy ten cheap 1U servers, four higher performance 2U, one “low cable count” blade chassis, or two high-end servers to satisfy the needs of your services?

A highly available service can be set up with cheap and simple server nodes, as Google and many others show us every day. On the flipside of the coin, you might be able to consolidate all your services on just a few high-end machines, reducing the management costs while at the same time taking advantage of the advanced RAS features these kind of machines offer. It takes a detailed study to determine which strategy is the best one for your particular situation, so we are not saying that one strategy is better than all the others. The point is that the choice between cheap clustered nodes and only a few high-end machines cannot be answered by simply looking at the size of the company you are working for or the "mission critical level" of your service. There are corner cases where the choice is clear, but that is not the case for the majority of virtualized datacenters.

So is buying high-end servers as opposed to buying two or three times more 2-socket systems an interesting strategy for your virtualized cluster if you are not willing to pay a premium for RAS features? Until very recently, the answer was simple: no. High-end quad socket systems were easily three times and more as expensive and never offered twice as much performance compared to dual socket systems. There are many reasons for that. If we focus on Intel, the MP series were always based on mature but not the cutting edge technology. Also, quad socket systems have more cache coherency overhead, and the engineering choices favor reliability and expandability over performance. That results in slower but larger memory subsystems and sometimes lower clock speeds too. The result was that the performance advantage of the quad system was in many cases minimal.

At the end of 2006, the Dual Xeon X5300 were more than a match for the Xeon X7200 quad systems. And recently, dual Xeon 5500 servers made the massive Xeon 7400 servers look slow. The most important reason why these high-end systems were still bought were the superior RAS features. Other reasons include the fact that some decision makers never really bothered to read the benchmarks carefully and simply assumed that a quad system would automatically be faster since that is what the OEM account manager told them. You cannot even blame them: a modern CIO has to bury his head in financial documents, must solve HR problems, and is constantly trying to explain to the upper management why the complex IT sytems are not aligned with the business goals. Getting the CIO down from the “management penthouse” to the “cave down under”, also called the datacenter, is no easy task. But I digress.

Virtualization can shatter the old boundaries between the midrange and high-end servers. They can be interesting for the rest of us, the people that do not normally consider these high-end expensive systems. The condition is that the high-end systems can consolidate more services than the dual socket systems, so performance must be much better. How much better? If we just focus on capital investment, we get the figures below.

Type Server CPUs Memory Approx. Price
Midrange Dell R710 2x X5670 18 x 4GB = 72GB $9000
Midrange Dell R710 2x X5670 16 x 8GB = 128GB $13000
High-end Dell R910 4x X7550 64 x 4GB = 256GB $32000

So these numbers seem to suggest that we need 2.5 to 3 times better performance. In reality, that does not need to be the case. The TCO of two high-end servers is most likely a bit better than that of four midrange servers. The individual components like the PSU, fans, and motherboard should be more reliable and thus result in less downtime and less time spent on replacing those components. Even if that is not the case, it is statistically more likely that a component fails in a cluster with more servers, and thus more components. Less cables and less hypervisor updates should also help. Of course, the time spent in managing the VMs is probably more or less the same.

While a full TCO calculation is not the goal of this article, it is pretty clear to us that a high-end system should outperform the midrange dual socket systems by at least a factor two to be an economical choice in a virtualization cluster where hardware RAS capabilities are not the only priority. There is a strong trend that the availability of the (virtual) machine is guaranteed by easy to configure and relatively cheap software techniques such as VMware’s HA and fault tolerance. The availability of your service is then guaranteed by using application level high availability such as Microsoft’s clustering services, load balanced web servers, Oracle fail-over, and other similar (but still affordable) techniques.

The ultimate goal is not keeping individual hardware running but keeping your services running. Of course hardware that fails too frequently will place a lot of stress on the rest of your cluster, so that is another reason to consider this high-end hardware... if it delivers price/performance wise. Let us take a closer look at the hardware.

The 32-Core, 64-Thread Beast
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  • blue_falcon - Tuesday, August 10, 2010 - link

    The R715 is an AMD box. Reply
  • webdev511 - Tuesday, August 10, 2010 - link

    Yes, and the R715 has 2x AMD Opteron™ 6176SE, 2.3GHz with 12 cores per socket with an approx price of $8,000 Reply
  • fic2 - Tuesday, August 10, 2010 - link

    4. Part of the Anandtech 13 year anniversary giveaway?!! ;o) Reply
  • mino - Wednesday, August 11, 2010 - link

    Big Thanks for that ! Reply
  • Etern205 - Tuesday, August 10, 2010 - link

    *stares at cpu graph*
    ~Drrroooollllliiiieeeeeeee~~~~
    Reply
  • yuhong - Tuesday, August 10, 2010 - link

    The incorrect references to Xeon 7200 should be Xeon 7100.
    "Other reasons include the fact that some decision makers never really bothered to read the benchmarks carefully"
    You didn't even need to do that. Knowing the difference between NetBurst vs Core 2 vs Nehalem would have made it obvious.
    Reply
  • ELC - Tuesday, August 10, 2010 - link

    Isn't the price of software licenses a major factor in the choice of optimum server size? Reply
  • webdev511 - Tuesday, August 10, 2010 - link

    So does the NUMA barrier.

    I'd go for less sockets with more cores any day of the week and as a result Intel= second string.
    Reply
  • Ratman6161 - Wednesday, August 11, 2010 - link

    For the software licensing reasons I mentioned above, there is a distinct advantage to fewer sockets with more cores. Reply
  • davegraham - Wednesday, August 11, 2010 - link

    so NUMA is an interesting one. Intel's QPI bus is actually quite good and worth spending some time to get to know.

    dave
    Reply

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