Performance Considerations when running Nutanix on vSphere

Here are some performance considerations for running Nutanix AOS 5.10 or higher on vSphere 6.7 U3b.

In vSphere 6.7 you may have noticed the introduction of Skyline Health (vSphere Client, vCenter Server object, Monitor, Skyline Health) and the reporting of the Compute Health Checks. You may have also noticed the informational alert in the ESXi summary tab that L1TF is present (vSphere Client, ESXi object, Summary tab). This is the VMware alert to mitigate CVE-2018-3646, a vulnerability in Intel processors; VMware KB 55636 covers it in detail. All of the other Skyline Health Compute Health Check alerts can be mitigated by using vUM to apply the latest ESXi security patches/ESXi driver updates and using Nutanix LCM to apply the latest Firmware updates.

In the screenshots below (via Nutanix X-Ray), the Random Write IOPS values (this metric correlates to CPU performance) for a Nutanix on vSphere cluster with SCAv2 enabled and disabled; if you do that math it is a 10% performance drop as advertised in VMware KB 55806. SCAv1 is a 30% CPU performance impact. If your organization deems L1TF to be a vulnerability that must be mitigated, build it into your cluster sizing calculations. Also consult with Nutanix Support on the correct CVM vCPU sizing, since Nutanix Sizer and Nutanix Foundation do not account for it.

If you decide to leave CVE-2018-3646 unresolved, you will have to delete the “Warning” Rule from the vSphere Health Alarm Definition (vSphere Client, vCenter Server object, Configure, Alarm Definitions, Filter “vSphere Health”, Edit), this removes the continuous “vSphere Health detected new issues in your environment” warning from vCenter Server (but leaves the “Critical” Rule in play). It is not possible to disable specific items from Skyline Health in vSphere 6.7, although you can disable Skyline Health entirely by leaving the CEIP.

If you have a node with 6-cores per socket (possibly to mitigate application licensing costs), be aware that Nutanix Foundation will deploy an 8 vCPU CVM that exceeds the NUMA boundaries of the 6-core Intel socket. Work with Nutanix Support to configure the “numa.nodeAffinity” setting for each Nutanix CVM.

Nutanix on vSphere must use NFSv3 Datastores. Make sure you account for the fact that the NFSv3 software in VMware vSphere 6.7 has a read performance limitation per host (approx. 130K Random Read IOPS @ 8K and approx. 2.12 GB/s Sequential Read @ 1M.). This can be mitigated by adding a second Datastore and spreading the vDisks of a Monster VM across two Datastores. You can also choose to use Nutanix Volume Groups instead of VMDKs (Guest OS iSCSI Initiator required with a Data Services IP on the Nutanix AOS cluster).

One Reply to “Performance Considerations when running Nutanix on vSphere”

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