A virtual volumes-based storage system provides protocol endpoints that are discoverable on the physical storage fabric. ESXi hosts use the protocol endpoints to connect to virtual volumes on the storage. Operation of the protocol endpoints depends on storage protocols that expose the endpoints to ESXi hosts.
Virtual Volumes supports NFS version 3 and 4.1, iSCSI, Fibre Channel, and FCoE.
No matter which storage protocol is used, protocol endpoints provide uniform access to both SAN and NAS storage. A virtual volume, like a file on other traditional datastore, is presented to a virtual machine as a SCSI disk.
A storage container is dedicated to SCSI or NAS and cannot be shared across those protocol types. An array can present one storage container with SCSI protocol endpoints and a different container with NFS protocol endpoints. The container cannot use a combination of SCSI and NFS protocol endpoints.
Virtual Volumes and SCSI-Based Transports
On disk arrays, virtual volumes support Fibre Channel, FCoE, and iSCSI protocols.
When the SCSI-based protocol is used, the protocol endpoint represents a proxy LUN defined by a T10-based LUN WWN.
As any block-based LUNs, the protocol endpoints are discovered using standard LUN discovery commands. The ESXi host periodically rescans for new devices and asynchronously discovers block‐based protocol endpoints. The protocol endpoint can be accessible by multiple paths. Traffic on these paths follows well‐known path selection policies, as is typical for LUNs.
On SCSI-based disk arrays at VM creation time, ESXi makes a virtual volume and formats it as VMFS. This small virtual volume stores all VM metadata files and is called the config‐VVol. The config‐VVol functions as a VM storage locator for vSphere.
Virtual volumes on disk arrays support the same set of SCSI commands as VMFS and use ATS as a locking mechanism.
Virtual Volumes and NFS Transports
With NAS storage, a protocol endpoint is an NFS share that the ESXi host mounts using IP address or DNS name and a share name. Virtual Volumes supports NFS version 3 and 4.1 to access NAS storage. Both IPv4 and IPv6 formats are supported.
No matter which version you use, a storage array can provide multiple protocol endpoints for availability purposes.
In addition, NFS version 4.1 introduces trunking mechanisms that enable load balancing and multipathing.
Virtual volumes on NAS devices support the same NFS Remote Procedure Calls (RPCs) that ESXi hosts use when connecting to NFS mount points.
On NAS devices, a config‐VVol is a directory subtree that corresponds to a config‐VVolID. The config‐VVol must support directories and other operations that are necessary for NFS.