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Fault Tolerance Performance in vSphere 6

VMware has published a technical white paper about vSphere 6 Fault Tolerance architecture and performance. The paper describes which types of applications work best in virtual machines with vSphere FT enabled.

VMware vSphere Fault Tolerance (FT) provides continuous availability to virtual machines that require a high amount of uptime. If the virtual machine fails, another virtual machine is ready to take over the job.  vSphere achieves FT by maintaining primary and secondary virtual machines using a new technology named Fast Checkpointing. This technology is similar to Storage vMotion, which copies the virtual machine state (storage, memory, and networking) to the secondary ESXi host. Fast Checkpointing keeps the primary and secondary virtual machines in sync.

vSphere FT works with (and requires) vSphere HA—when an administrator enables FT, vSphere HA selects the secondary VM (admins can vMotion the VM to another server if needed). vSphere HA also creates a new secondary if the primary fails—the original secondary becomes the new primary, and vSphere HA selects an available virtual machine to use as the new secondary.

vSphere 6 FT supports applications with up to 4 vCPUs and 64GB memory on the ESXi host. The performance study shows results for various workloads run on virtual machines with 1, 2, and 4 vCPUs.

The workloads—which tax the virtual machine’s CPU, disk, and network—include:

  • Kernel compile – loads the CPU at 100%
  • Netperf-  measures network throughput and latency
  • Iometer- characterizes the storage I/O of a Microsoft Windows virtual machine
  • Swingbench- drives an OLTP load on a virtual machine running Oracle 11g
  • DVD Store –  drives an OLTP load on a virtual machine running Microsoft SQL Server 2012
  • A brokerage workload – simulates an OLTP load of a brokerage firm
  • vCenterServer workload – simulates actions performed in vCenter Server

Testing shows that vSphere FT can successfully protect a number of workloads like CPU-bound workloads, I/O-bound workloads, servers, and complex database workloads; however, admins should not use vSphere FT to protect highly latency-sensitive applications like voice-over-IP (VOIP) or high-frequency trading (HFT).

For the results of these tests, read the paper. Also useful is the VMware Fault Tolerance FAQ.

3 thoughts on “Fault Tolerance Performance in vSphere 6

  1. Ross Warner

    Our primary application is a small SQL installation with 5 Users. It is a 911 Dispatch environment. With FT on, Dispatch staff can notice 1/2 to 3 second delays in screen input. Without FT everything runs fine without delays. We purchased into VMware particularly with the intent to use FT. Will there Ever Be a better environment with FT (without latency) than there is now? Can we Ever expect FT to work in a latency sensitive environment?

  2. Don Johnson

    Same Problem like Ross, here with vSphere 6.0U2 and vSAN. We have vmkernel for FT and vMotion with 10Gb Links, the VM is 1Gb connected.

    Network throughput without FT: ~80 MByte/s
    Network throughput with FT: ~2 MByte/s

    Latency without FT: <1ms
    Latency with FT: between 10ms and 200ms

    The VM is Server2012R2 without any workload! It's unusable….

  3. Yiting Jin

    Hi Ross and Don, we will be sharing some “tech preview” performance data in a breakout session at VMworld in Las Vegas. Will you be there? We’ve made some significant improvements to FT for workloads that are more susceptible to latency increases, so while there is still some performance overhead, you will see better performance vs. what you did in vSphere 6.

    Are you using 10Gb NICs for the FT logging network, separate from the management or vMotion networks? Which Intel / AMD processor generations? Happy to do a call with you and our engineering team to discuss these specific cases. Please email me at yitingjin@vmware.com if you’re interested in setting up a discussion.


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