Named disks are standalone virtual disks that you create in organization virtual data centers (VDCs). Organization administrators and users who have the necessary rights can create, remove, and update named disks, and connect them to virtual machines.
When you create a named disk, it is associated with an organization VDC but not with a VM. After you create the disk in a VDC, the disk owner or an administrator can attach it to any VM deployed in the VDC. If you have the Organization VDC Shared Named Disk: Create right in the VMware Cloud Director API or Create a Shared Disk right in the UI, you can create a shared named disk that you can attach to multiple VMs. The disk owner can also modify the disk properties, detach it from a VM, and remove it from the VDC. System administrators and organization administrators have the same rights to use and modify the disk as the disk owner.
- The disk sharing type creates an underlying independent persistent disk in vSphere with multi-writer mode enabled. The multi-writer option shares the named disk at the disk level so that multiple VMs across up to eight hosts can lock it at the same time. You cannot use Windows Server Failover Cluster (WSFC) configurations with disk level sharing.
- The controller sharing type creates a shared disk through physical SCSI bus sharing and supports configurations like WSFC. With the controller level sharing, up to eight VMs can access the same virtual disk or Raw Disk Mapping (RDM) simultaneously. A Windows cluster can have up to five VMs. To avoid simultaneous writes, the guest OS functionality chooses the node that can write on the shared disk.
If you attach a named disk, you cannot take VM snapshots. If a shared disk is attached to a VM, you cannot edit its hard disk setting from the VM details view.
If the organization VDC has a storage policy with enabled VM encryption, you can encrypt VMs and disks by associating them with storage policies that have the VM Encryption capability. See Virtual Machine Encryption.