This post was authored by Mike McGhee, Technical Marketing Engineer at Nutanix
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 Acropolis Block Services (ABS), where Nutanix storage is presented directly to VMs using the iSCSI protocol. The storage is allocated using Nutanix Volume Groups and attached to the VMs using ABS and 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 ABS devices directly to an ESXi host.
When using ESXi as the hypervisor, leverage volume groups and in-guest iSCSI (which equals ABS) to directly present vDisks to the VMs, and you'll be in a supported configuration.
For Hyper-V, Nutanix also supports the use of ABS to provide shared storage for WSFC. Just like with ESXi, you would use ABS 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 options 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 or Windows 2016.
With Windows 2016 and Hyper-V, Microsoft has introduced another shared virtual disk option known as VHD sets. Nutanix does not currently support VHD sets with Windows 2016, so stick with shared virtual hard disks and you'll be good to go.
With AHV, Nutanix requires the use of ABS for WSFC support. Same as with ESXi and Hyper-V, create a volume group and attach it directly to the Windows VMs using in-guest iSCSI. For those familiar with volume groups on AHV, there is a second method for presenting volumes groups to VMs, known as a direct attach. Direct attaching volume groups is currently 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 does not enable support for SCSI-3 persistent reservations. Further, the bus type discovered by Windows when direct attaching a volume group is blocked for use by WSFC for shared disks. Nutanix is planning support for WSFC shared storage when direct attaching a VM to a volume group in a future release.
Hopefully this helps clear up any confusion over how Nutanix supports shared storage for Windows Failover Clusters today. Please see the ABS Best Practices Guide
for how to use ABS 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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