by Avinash Nayak

The good folks in Oracle’s marketing department deserve a raise for their efforts around promoting the latest release of the company’s virtualization solution, Oracle VM (OVM) 3. They certainly are aiming high, claiming OVM 3 is four times more scalable than VMware, four times cheaper to deploy than VMware, and is architected for efficiency while VMware is prone to inefficiencies. Not bad for a product that did not even exist until 2009 and is only on its second release (why the second release is called OVM 3, I don’t know). Unfortunately for Oracle Marketing, there’s a problem, namely – the FACTS. The facts show that VMware vSphere 5 delivers much higher scalability, greater value and unmatched performance compared to OVM.

Let’s take a closer look at Oracle’s claims and compare them with the facts:

Is OVM 3 four times more scalable than VMware? Switch the order of the products and it's perfect.

Oracle bases this claim on the fact that OVM 3 supports 128 virtual CPUs (vCPUs) per VM, where vSphere 5 VMs support 32 vCPUs.

Wait. Did someone change the definition of scalability when we weren’t looking? Since when is the scalability of a virtualization platform defined only by the number of VM vCPUs supported?

Surely, a better measure of the scalability of a platform is the number of VMs doing useful work that the platform can support (and manage) on a host or a cluster. It’s not the only measure, but one that’s far more insightful for showing scalability than just comparing vCPUs. Oracle’s documentation shows that OVM 3 is only able to run up to 128 VMs per host, compared to 512 for vSphere 5 (four times more than OVM 3, what a coincidence). So, it looks like Oracle got the “four times” part right. They just got the products mixed up. Simple mistake.

In addition, VMware’s testing has shown that a 32 vCPU guests can deliver 92-97% of native performance. Oracle has yet to provide any evidence that a 128 vCPU guest can scale linearly on OVM3.0.

Is VMware four times more expensive than OVM 3? NO. Maybe Oracle meant vSphere has four times more functionality than OVM 3.

Oracle makes this claim solely based on virtualization software costs. But virtualization software cost is only one component of the total cost of deploying an application. The other components are the hardware costs (server, storage and networking), guest OS licensing costs, power and datacenter space costs. You need to take into account all of these when calculating the total costs for deploying an application.

Thanks to the advanced features provided by vSphere, customers are able to realize significant savings from reduction in hardware necessary to deploy an application environment relative to OVM.  Through the use of multiple advanced memory management features  (transparent page sharing, ballooning, memory compression, and hypervisor swapping), vSphere is able to achieve much greater VM density per host than OVM, meaning you need fewer hosts to deploy the same number of VMs. Independent tests have shown that vSphere 5 consistently delivers higher VM density compared to competing platforms, such as Xen based OVM.

Let’s take a simple example and compare the TOTAL cost of deploying 100 Linux VMs on vSphere 5 Enterprise Plus (VMware’s highest vSphere edition) vs. OVM3. We assume a conservative 25% density advantage for vSphere over OVM. This means that if we assume we deploy 12 VMs per host for OVM, we can deploy 15 VMs per host for vSphere 5.


We see that even the highest edition of vSphere 5 is less than 6% more expensive than OVM when you take into account TOTAL cost. So it appears that Oracle’s cost claims are exaggerated by 400/6 = 66.67 times.

So what do you get for a premium of less than 6%? Here’s a subset of the features found in vSphere 5 that are absent from OVM:



VMware vSphere 5 

Oracle VM 3

Clustered File System

VMFS 5 Purpose built and tested for virtualization

OVM built on OCFS2, not built for virtualization

Thin, bare-metal hypervisor

Yes, ESXi has a small 144MB footprint for better reliability and security

No, OVM 3’s Xen hypervisor requires a large Linux management partition making it four times larger

Logical resource pools

Yes, divide and assign cluster resources to hierarchical groups

No, users share all resources across entire server pool

Role-based access controls

Extensive customizable user roles and permissions

No, single user account used for all hosts managed by OVM Mgr

Storage live migration

Storage vMotion


Storage array support

Supports over 1,200 arrays, vSphere Storage APIs for Array Integration supported by 175 arrays

Storage Connect API supported by less than 20 arrays

Auto storage tiering

Profile-Driven Storage


Thin disks

Fully supported


Broad guest OS support

Over 88 guests

Only 13 guests

Complete resource balancing

DRS and Storage DRS, balances memory, CPU, storage load

DRS feature considers only CPU and network load

“Noisy neighbor” protection

Yes, Network and Storage I/O Controls


 HA policy enforcement 

 HA supports: admission controls, VM-VM affinity/anti-affinity controls, restart priority 

 HA feature supports only basic restart ; Only anti-affinity controls

Memory overcommit

Yes, enables greater VM density, lower costs


But Oracle should be intimately familiar with how a “free” solution does not necessarily provide better value. After all, isn’t MYSQL a free product (like OVM) and you only pay for support. Does it deliver the same capabilities as Oracle’s Enterprise Database solutions? I wonder what Oracle has to say about that.

Is OVM 3 more efficient than vSphere? We’d like to see the evidence.

The basis for this claim is a four year old Oracle VM Benchmark Performance Report from The Tolly Group done using OVM 2 (the first version of the product). The performance tests compare OVM 2 (note – Not OVM 3) to physical servers, not to vSphere. Oracle has not provided any evidence to support the claim that OVM 3 is more efficient or has a performance advantage over vSphere.

Like other Xen-based hypervisors, Oracle VM requires guest operating systems with extensive Xen paravirtualization modifications to get acceptable performance. Instead, vSphere uses unmodified guest OSs together with optimized device drivers and full support for virtualization hardware assist features in modern processors to deliver unmatched performance. This approach allows customers to use standard operating systems that are fully supported by ISVs. And with a disk footprint of only 144MB, the vSphere hypervisor represents a far smaller attack surface. An OVM 3 server’s disk footprint is swollen to 588MB (four times larger than vSphere) by the Linux management operating system installed in the Dom0 partition.

Also, without advanced features like Network and Storage I/O Controls, OVM is unable to guarantee service levels for business critical applications (for example, large databases.) vSphere is the only platform that delivers capabilities to ensure that your most important applications have access to the resources they need to meet required SLAs.

Grading the claims made by Oracle with regards to OVM 3:

Marketing: PASS; Delivering on the Marketing Claims: FAIL

So it looks like VMware will not be shutting shop just yet. Despite what Oracle says, vSphere 5 is well ahead of OVM 3 in terms of performance, features and value.

This blog is part of a series on Virtualizing Your Business Critical Applications with VMware. To learn more, including how VMware customers have successfully virtualized SAP, Oracle, Exchange, SQL and more, visit