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Comparing ESXi 4.1 and ESXi 5.0 Scaling Performance

In previous articles on VROOM! we used VMmark 2 to investigate the effects of altering a single hardware component, such as a storage array or server model, in a vSphere cluster. In contrast to these earlier studies, we now examine the effects of upgrading the hosts’ software from ESXi 4.1 to ESXi 5.0 on the performance of a VMmark 2 cluster.

vSphere 5 includes many new features and virtual machine enhancements, the details of which can be found here. To the IT professional weighing the costs and benefits of upgrading their existing infrastructure to vSphere 5, an often important question is whether ESXi 5.0 can outperform ESXi 4.1 in the same environment. VMmark 2 is an ideal tool for answering this question with measurable results. We used VMmark 2.1.1 to see how ESXi 5.0 stacked up to ESXi 4.1 on an identically configured cluster.

VMmark 2 is a multi-host virtualization benchmark that models application performance as well as the effects of common infrastructure operations such as vMotion, Storage vMotion, and virtual machine deployments. Each VMmark tile contains a set of VMs running diverse application workloads as a unit of load. VMmark 2 scores are computed as a weighted average of application workload throughput and infrastructure operation throughput. For more details, see the overview, release notes for VMmark 2.1, and for 2.1.1.

Testing Methodology

All VMmark 2 tests were conducted on a cluster of four identically configured entry-level Dell Power Edge R310 servers. To determine the impact of the vSphere 5 environment on performance, a series of tests was conducted with these hosts running ESXi 4.1, then with ESXi 5.0. In addition, for the vSphere 5 environment, the virtual machine hardware and VMware Tools were upgraded on all workload VMs, and LUNs were reformatted as VMFS5. All other components in the environment remained unchanged during testing.

Configuration
Systems Under Test: Four Dell PowerEdge R310 Servers
CPUs: One Quad-Core Intel® Xeon® X3460 @ 2.8 GHz, hyper-threading enabled per server
Memory: 32GB DDR3 ECC @ 800 MHz per server
Storage Array: EMC VNX5500
Hypervisors under test:
VMware ESXi 4.1
VMware ESXi 5.0
Virtualization Management: VMware vCenter Server 5.0
VMmark version: 2.1.1

Results

To characterize cluster performance at multiple load levels, we increased the number of tiles until the cluster reached saturation, defined as when the run failed to meet Quality of Service (QoS) requirements. Scaling out the number of tiles until saturation allows us to determine the maximum VMmark 2 load the cluster could support and to compare the ESXi 4.1 and ESXi 5.0 configurations at each level of load.

The graph below shows the results of the VMmark 2 testing as described above with identically configured clusters running ESXi 4.1 and ESXi 5.0. All data points are the mean of three tests in each configuration.

  Scaling

 

The ESXi 4.1 cluster reached saturation at 3 tiles, but ESXi 5.0 was able to support 4 tiles while still meeting workload Quality of Service requirements. The ESXi 5.0 cluster also outperformed ESXi 4.1 by 3% and 4% on the two and three-tile runs, respectively. Differences in CPU utilization were negligible. The results show that, in an equivalent environment, vSphere 5 handled greater load than ESXi 4.1 before reaching saturation, and showed increased performance at lower levels of load as well. At saturation, vSphere 5 showed a 22% increase in overall VMmark 2 scores over ESXi 4.1. In this cluster, vSphere 5 supported 33% more VMs and twice the number of infrastructure operations while meeting Quality of Service requirements.

VMmark 2 scores are based on application and infrastructure workload throughput, while application latency reflects Quality of Service. For the Mail Server, Olio, and DVD Store 2 workloads, latency is defined as the application’s response time. The completion time for vMotion, Storage vMotion, and VM Deploy is used as the latency measurement for the infrastructure operations. Latency can be very informative about the functioning of the environment and how the cluster as a whole performs under increasing loads. Examining latency at a 3-tile load, as seen in the figure below, reveals significant differences between the hypervisor versions. Latencies were normalized to the ESXi 4.1 results.

Latency

We saw decreases in latency for all VMmark 2 workloads with vSphere 5. The latency decreases were most striking in Olio, Storage vMotion, and DVD Store 2, with decreases of 20%, 19%, and 15%, respectively. These improvements to vMotion and Storage vMotion are consistent with publicized improvements in vMotion and Storage vMotion latency for vSphere 5 (details here).

A VMmark 2 run passes when all of its application QoS metrics, or latencies, remain below a specified threshold. These decreases in latency with ESXi 5.0 are directly related to why ESXi 5.0 was able to support an additional tile relative to ESXi 4.1.

Our comparison has shown that upgrading an ESXi 4.1 cluster to vSphere 5 had two high-level effects on performance. The vSphere 5 cluster supported 33% more VMs at saturation than the ESXi 4.1 cluster, and it also exhibited improved latency and throughput at lower levels of load, showing that ESXi 5.0 does outperform ESXi 4.1.

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