WSFC/MSCS vSphere 6.x Enhancements

For those that aren’t aware, VMware released an updated Microsoft WSFC Setup and Deployment Guide for vSphere 6.x.
In a previous blog post I covered Microsoft Clustering Design Implications in vSphere 5.x. Fundamentally the deployment of WSFC has not changed significantly. However, there are a couple of new features that I wanted to cover here.
New Features and Requirements:
  • vMotion supported for cluster of virtual machines across physical hosts (CAB deployment) with passthrough RDMs. Note, you must use VM-hardware version 11.
    • VMware recommends updating the heart-beat timeout ‘SameSubnetThreshold’ registry value to 10. Additional info can be found on MS Failover Clustering and NLB Team Blog and in VMware’s updated WSFC Setup and Deployment Guide.
    • The vMotion network must be a 10Gbps.
      • 1Gbps Ethernet link for vMotion of MSCS virtual machines is not supported.
        • Fair enough, but most customer deployments using 10GbE also share that with other workloads. In addition using NIOC to prioritise traffic to prod workloads. So its not clear if the minimum requirement is 10GbE or higher bandwidth that can be provided by 1GbE.
    • vMotion is supported for Windows Server 2008 SP2 and above. Windows Server 2003 is not supported.
    • SCSI bus sharing mode set to Physical.
  • ESXi 6.0 supports PSP_RR for Windows Server 2008 SP2 and above releases (same as ESXi 5.5 but with restrictions)
    • Shared disk quorum or data must be provisioned to guest in PassThrough RDM mode only
  • All hosts must be running ESXi 6.x
    • Mixed mode operating with older ESXi revisions not supported.
    • Rolling upgrades of cluster hosts from previous versions of ESXi to ESXi 6.x is not supported.
  • MSCS (Windows Server Failover Clustering (WSFC)) is supported with VMware Virtual SAN (VSAN) version 6.1 and later. See VSAN 6.1 Whats New!.
  • In vSphere 6.0, VMware introduced support for using Windows Server Failover Clustering or Microsoft Server Failover Clustering to protect a Windows-based vCenter Server.
  • Modifying the MSCS heartbeat time-out: An MSCS virtual machine can stall for a few seconds during vMotion. If the stall time exceeds the heartbeat time-out interval, then the guest cluster considers the node down and this can lead to unnecessary failover.
    • VMware recommends changing the DWORD ‘SameSubnetThreshold’ registry value in each WSFC node to 10.
  • VMware also warns of deploying WSFC in vSphere environments with memory overcommitment. Memory overcommitment (worse active memory reclamation like compression, swapping) can cause virtual machine I/O latency to increase, potentially causing failover. Set memory reservations if you are concerned this may affect your WSFC/MSCS nodes.

Not Supported / Limitations:

  • No Storage vMotion for VMs that are configured with shared disks.
  • No support for WSFC on NFS.
  • Running WSFC nodes on different ESXi versions (Pity as this would have been ideal for ESXi 5.x to ESXi 6.x upgrades).
  • Cant use WSFC in conjunction with VMware FT.
  • NPIV not supported.
  • Server 2012 storage spaces not supported.