This post was authored by Mike McGhee, Technical Marketing Engineer at Nutanix
This post was updated June 9, 2020
One of the frequently asked questions we receive is how to create Windows Server Failover Clusters (WSFC) within virtual machines (VM) running on Nutanix. The purpose of this post is to detail our shared storage support for WSFC.
Nutanix supports WSFC within VMs on AHV, ESXi and Hyper-V. Within this support, WSFC can have both shared storage and non-shared storage. Some application clustering solutions that work with WSFC do not require shared storage. Some examples include Exchange Database Availability Groups (DAG) and SQL Server Always-On Availability Groups (AAG). For non-shared storage, any virtual disk type supported by Nutanix based on the specific hypervisor can be used.
For clusters that need shared storage, such as clustered file servers or SQL Server Failover Cluster Instances (FCIs), Nutanix requires specific storage configurations for WSFC. Shared storage requires disk types that supports both sharing and SCSI-3 persistent reservations. The supported configuration varies somewhat, depending on the underlying hypervisor used by the VMs.
For ESXi, Nutanix requires the use of Nutanix Volumes, where storage is presented directly to VMs using the iSCSI protocol. The storage is allocated using Nutanix Volume Groups and attached to the VMs using the iSCSI Software Initiator within Windows.
Many vSphere administrators are familiar with forming VM based clusters by leveraging Raw Device Mappings (RDM) by first presenting shared storage to ESXi, and then via an RDM to the VM. The use of RDMs are not supported with Nutanix. Further we do not support presenting Nutanix Volumes based devices directly to an ESXi host.
When using ESXi as the hypervisor, leverage volume groups and in-guest iSCSI (which equals Nutanix Volumes) to directly present vDisks to the VMs, and you'll be in a supported configuration.
For Hyper-V, Nutanix also supports the use of Nutanix Volumes to provide shared storage for WSFC. Just like with ESXi, you would use Nutanix Volumes to present storage directly to the VMs using Volume Groups and in-guest iSCSI. Hyper-V also has another option. Nutanix supports the use of shared virtual hard disks to provide shared storage for WSFC when the VMs run on Hyper-V. This option lets you utilize the native Nutanix SMB share to create virtual disks both accessible by multiple VMs and which support SCSI-3 persistent reservations. Nutanix supports shared virtual hard disks where the underlying version of Hyper-V leverages either Windows 2012 R2, Windows 2016 or Windows 2019.
With Windows 2016 and Hyper-V, Microsoft had introduced another shared virtual disk option known as VHD sets. Nutanix does not currently support VHD sets with Windows 2016 or Windows 2019, so stick with shared virtual hard disks and you will be good to go.
With AHV, Nutanix supports the use of Nutanix Volumes for WSFC support. Same as with ESXi and Hyper-V, create a volume group and attach it to the Windows VMs using in-guest iSCSI.
For those familiar with volume groups on AHV, there is a second method for presenting volume groups to VMs, known as a direct attach. Directly attaching volume groups, prior to the AOS 5.17 release, was not supported for the shared storage needed by WSFC. While directly attaching VMs to a volume group allows for shared storage (say when using Oracle RAC), this storage did not enable support for SCSI-3 persistent reservations. With the AOS 5.17 release, in combination with AHV version AHV-20190916.189 and Nutanix VirtIO driver version 1.1.4 or higher, WSFC with AHV are supported with directly attached volume groups. .
Hopefully this helps clear up any confusion over how Nutanix supports shared storage for Windows Failover Clusters today. Please see the Nutanix Volumes Best Practices Guide for how to present storage to the Windows OS for the purpose of clustering. If you're planning on using Microsoft SQL Server, we have a best practices guide for SQL as well. Please post below if you have any additional questions or concerns..
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