VMware Cost-Per-Application Calculator

In evaluating the cost of a virtualization solution, it is essential to use a metric that not only looks at the cost of licensing the virtualization software, but also takes into account other infrastructure components such as servers, networking, storage, power, real estate and guest operating systems licensing. The costs associated with these elements are directly dependent on the number of applications per server that a virtualization solution can run simultaneously (also known as virtual machine density). In addition, because centralized management is a fundamental component of any virtualization deployment, hardware and software costs associated with related management products, such as VMware vCenter or Microsoft System Center need to be included as well.

VMware defines cost-per-application as the sum of all these cost items divided by the number of applications virtualized:

VMware Cost-Per-Application Calculator does not provide a full TCO analysis as it 1) does not account for opex savings and 2) is not a multi-year analysis that accounts for depreciation of hardware equipment over its life-cycle. The Cost-Per-Application Calculator provides a simple and accurate way to estimate the upfront capital expenditure required for deploying a virtualization platform. For a full TCO analysis of VMware vSphere 4 that accounts for both operational savings and equipment life-cycle refer to the VMware TCO Calculator.

Due to its advanced technologies and architecture, VMware vSphere 4 makes it possible to successfully run more applications per host (physical server) and to achieve higher VM density than other solutions. Consequently VMware vSphere 4 delivers a lower cost per application than Microsoft Windows Server 2008 (Hyper-V) + Systems Center. The most significant reasons why VMware vSphere can enable a higher VM density per host include the following:

1. Memory Oversubscription – VMware ESX makes more efficient use of physical RAM by reclaiming unused physical memory allocated to particular VMs (think of it as de-duplication for memory) and consolidating identical memory pages among VMs on a host. Both functions let ESX oversubscribe memory on a server with minimal impact to performance. This memory oversubscription is no different than oversubscribing the CPU and network on a virtual host. Other solutions, such as Microsoft Windows Server 2008 (Hyper-V), lock the memory assigned to a VM so that no other VM can use it, regardless of whether the memory is being used or not. Locking memory assigned to a VM leads to very inefficient use of physical RAM and lowers the number of virtual machines that can be successfully hosted on a single virtualized server.
2. Direct Driver Model – VMware optimizes device drivers for virtualization and places them directly in the ESX hypervisor. By giving VMs direct and fast access to the hardware VMware ESX can achieve very high I/O throughput and can handle the I/O requirements for more VMs simultaneously requesting hardware resources. Other hypervisors, such as Hyper-V, use an indirect driver model that leverages the generic Windows device drivers, located in a separate partition (Parent Partition) of the virtualization software stack that contains an instance of Windows Server 2008. Microsoft’s “indirect” architecture single threads the I/O requests from all VMs through a single channel into the Parent Partition instance of Windows Server, forcing the VMs to fight over resources in the operating system. This creates an I/O bottleneck that reduces the I/O throughput Hyper-V can achieve; as more VMs are run on the same host, the I/O bottleneck gets worse. The Hyper-V indirect driver model also makes every VM reliant on third-party device drivers that have achieved only basic WHQL certification – Microsoft has no requirement for device drivers used with Hyper-V to be tested with a virtualized environment. That makes all your Hyper-V VMs dependent on the component of Windows known to be its weakest link – the device drivers.
3. High Performance "Gang" Scheduler – VMware designed and optimized the ESX process scheduler to handle the resource requirements of many heterogeneous VMs. Other hypervisors use the generic process scheduler of general purpose operating systems. These were not designed for virtualization nor do they meet the special needs of multiple VM workloads. Generic process schedulers, like the Windows scheduler used with Hyper-V, were designed to fulfill different use cases, such as providing an effective user interface experience. Because of its reliance on the Windows scheduler, Hyper-V gets hit by performance limits at levels far lower than those of VMware ESX and can run fewer VMs per host than VMware ESX. By comparison, the architecture of the ESX "Gang" scheduler is optimized for virtualization. It can dynamically account for the CPU and I/O needs of virtual machines by dynamically allocating more resources and larger processor timeslices to VMs.
4. Support for Large Memory Pages and Nested Page Tables – Large memory pages and nested page tables optimize memory access and can provide substantial performance benefits for mission critical, memory-intensive applications, such as an Oracle database. Large memory pages and nested page tables allow VMware solutions to achieve high levels of performance while consuming significantly fewer CPU resources. VMware ESX supports both features. Test results show that large memory pages and nested page tables can reduce CPU resource consumption by up to 15%. VMware ESX automatically redistributes the freed CPU power to other workloads, ultimately allowing higher VM density. On the other hand, Microsoft Windows Server 2008 (Hyper-V) does not support these features and consequently forces users to allocate more hardware resources and run them at a lower VM density than VMware ESX.
5. DRS with Resource Pools – VMware vSphere can dynamically load balance VMs across a cluster so applications get required resources when they need them. This reallocation of resources happens automatically and without service discontinuity, based on service levels set by the application owners. DRS is essentially a “safety net” that lets administrators run individual servers at higher utilization levels while meeting service level agreements—even when spikes occur. DRS lets usage spikes that might overwhelm a single server be leveled across many servers in a cluster with no interruption to the end user. Microsoft Windows Server 2008 (Hyper-V) does not have any comparable feature. The closest is its PRO Tips, but that is handicapped by its Quick Migration technology that forces downtime every time a virtual machine is migrated, resulting in unacceptable performance interruptions.

Bottom Line:

With these and other product advantages VMware customers report that with VMware Infrastructure 3 they could achieve 50-70% higher VM density per host than with Microsoft Windows Server 2008 (Hyper-V), resulting in a 20-30% lower cost-per-application on average. VMware vSphere 4 introduces significant improvements even over VMware Infrastructure 3 that will lead to even higher VM density and lower cost per application. However, VMware vSphere 4 will provide a lower cost-per-application than Microsoft Windows Server 2008 (Hyper-V) even at a similar VM density. We are currently testing VMware vSphere 4 RTM release and we will soon update the VMware Cost Per Application Calculator to reflect its enhanced capabilities.

Table 4 shows a detailed overview of the cost per application composition for the deployment you selected.

Table 4 – Detailed overview of the cost-per-application for virtualizing 100 applications

Assumes that a VMware ESX server can run 50% more applications than a Microsoft Windows Server 2008 (Hyper-V) host

Table 5 – Server Hardware

Table 6 – Storage Hardware

Table 7 – Networking Hardware

Table 8 – Power and cooling (Year 1)

Table 9 – Data Center Space (Year 1)

VMware virtualization and management software

Table 10 – VMware software

Windows operating system software

Table 11 – – Windows OS and SQL Server licensing cost for VMware solution

Table 12 – – Windows OS and SQL Server licensing cost for Microsoft solution

Table 13 – – Microsoft System Center and Microsoft management software

Note: Virtual Machine Manager 2008 can be licensed also in an enterprise standalone edition. Without Operations Manager and Configuration Manger, however, Virtual Machine Manager lacks several core management capabilities, which are instead available with VMware vCenter Server. In order to maintain fair apples-to-apples comparison, this model only presents comparisons between VMware vCenter Server and Virtual Machine Manager with Operation Manager and Configuration Manager.

For more details about the methodology and assumptions of the VMware Cost Per Application Calculator read this white paper.

Assumptions apply to both VMware and Microsoft.

For more details about the methodology and assumptions of the VMware Cost Per Application Calculator read this white paper.