Customers are often asking what server configuration they should choose for their virtualization environment. Do they go with a 2-socket multi-core based system, the traditional building block of the Data Center, or should they select a 4-socket server, which typically has more RAS features and better capacity in terms of cores, memory, and I/O better support their needs?  It’s kind of like choosing to go on vacation with that convertible you love to drive on the weekends or your trusty sedan that you go to work in every day! They both have their purpose but one may be better suited for the task at hand.

<!--more-->A recent survey conducted by Gabriel Consulting Group highlighted some interesting x86 server purchasing trends.  The largest market for x86 servers is still the 2-socket based servers, with almost 40% of the respondents saying they are planning on purchasing “more” or “many more” systems in the coming year.  But, the survey also reflected an increasing interest in 4-socket servers with 33% of the respondents saying they intend to purchase these systems in greater volumes.

A key driver in this trend towards larger servers is virtualization.  When it comes to virtualization, there are compelling advantages to be realized in implementing 4-socket or even 8-socket systems;
<ul>
	<li>Reduced hardware footprint. Particularly important for data centers that are space constrained and want to use fewer numbers of larger servers to consolidate both infrastructure and business application workloads.</li>
	<li>More cores. There is evidence that 2P servers can adequately support a large number of virtual machines running very light workloads where each virtual machine uses one or at most two virtual CPUs to get the job done.
<ul>
	<li>However, for more demanding workloads, the more virtual CPUs you can assign to each VM (in other words, the more cores you have available) the better each workload will run. It should be noted that VMware’s recently introduced vSphere product has increased capabilities to support up to 8 virtual CPUs per VM, anticipating the continued migration of more demanding, production-level applications to virtualized environments.</li>
	<li>A good example of this is seen in a paper highlighting the best practices for deploying Citrix XenApp with XenServer for HP ProLiant servers, where scalability is shown to degrade if you assign more virtual CPUs than there are physical CPU cores.</li>
</ul>
</li>
	<li>Larger memory footprint. The amount of memory available is particularly important for resource intensive workloads that process large amounts of information or stream data to many concurrent user sessions as is the case with a virtual desktop infrastructure. AMD OpteronTM processor-based 4-socket servers like the HP Proliant DL585 G5 and the Dell PowerEdge R905 can handle up to 256GB of memory per server while the HP Proliant DL785 and Sun Fire X4600 can handle up to 512GB of memory while 2-socket servers can only provide up to 144GB of memory.</li>
	<li>Additional headroom for peak workloads. Often more demanding workloads like transaction-based business applications have less predictable workloads that peak with high demand. The additional cores, memory, and I/O capabilities of 4-socket servers give you this scalability edge to handle these bursts.</li>
	<li>Consolidation of larger numbers of applications. While theoretically possible, most IT shops are currently not running hundreds of virtual machines on a single server. But, optimal virtual machine density is still a goal of many organizations implementing virtualization today. Four-socket servers provide a reliable and highly efficient platform for consolidation particularly for data intensive or more heavily utilized workload.</li>
</ul>
No discussion on the benefits of virtualization and 4-socket servers would be complete without addressing the aspect of ROI.  There is a fantastic article recently posted by Collin MacMillan that shows Shanghai Refresh Delivers ROI in 2-months using Intel’s ROI calculations for a Nehalem server replacement that yields an ROI in eight months.  Collin also references an Intel/IDC white paper that concludes, “Systems based on 4P platforms provide better consolidation ratios and scalability than 2P platforms.”

In the end it’s all about having the right balance of resources - CPU, memory, network and storage.  As system utilization increases to 50% or more through virtualization, there is an increased demand for balanced systems with the potential for providing higher levels of CPU and memory resources.

One thing is for sure, there is no one-size-fits-all when it comes to virtualization.  Customers are finding more and more workloads that are suitable for virtualization due to technology improvements like you see with AMD Opteron multi-core processors with AMD-VTM technology.  So which one is going to get you to your destination, the convertible or the SUV?