A Virtual Volumes 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.
Virtual Volumes and SCSI-Based Transports
On disk arrays, Virtual Volumes supports 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 supports the same set of SCSI commands as VMFS and use ATS as a locking mechanism.
CHAP Support for iSCSI Endpoints
Virtual Volumes supports Challenge Handshake Access Protocol (CHAP) with iSCSI targets. This support allows ESXi hosts to share CHAP initiator credentials with Virtual Volumes storage providers, also called VASA providers, and for Virtual Volumes storage providers to raise system events notifying vCenter Server of changes to CHAP target credentials on the storage array.
Each ESXi host can have multiple HBAs and each HBA can have properties configured on it. One of these properties is the authentication method that the HBA must use. Authentication is optional, but if implemented, it must be supported by both the initiator and target. CHAP is an authentication method that can be used both directions between initiator and target.
For more information about different CHAP authentication methods, see Selecting CHAP Authentication Method. To configure CHAP on your ESXi host, see Configuring CHAP Parameters for iSCSI or iSER Storage Adapters.
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 supports 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.