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Traditionally, VM data is stored as a collection of files on a VMFS or NFS datastore, which is a LUN or file system on the storage system. With Virtual Volume (vVol) datastores, each file is stored on a dedicated storage object, called a Virtual Volume, on the storage system. Dell Unity storage keeps track of the different types of vVols and maps them to the VM to which they belong. This enables data services to be applied only to the vVols that are associated with a particular VM, instead of all of the VMs on the entire datastore.
Depending on the type of data that is being stored on the vVol, a certain type of vVol is provisioned:
At a minimum, three vVols are required for each powered-on VM: data for the hard disk, config for the configuration, and swap for the memory pages. Unisphere provides a list of the vVols that exist on the system. This is only for visibility and troubleshooting purposes because the management of vVols is handled automatically. Dell Unity storage uses the VASA protocol to communicate with vSphere to create, bind, unbind, and delete vVols as needed. With the release of Dell Unity OE version 4.1.2, support has been expanded to include VASA 3.0. The Virtual Volumes page in Unisphere is shown in Figure 25.
Open the Properties page to view more details of each type of vVol as shown in Figure 26.
VMs could potentially utilize several more vVols, depending on the configuration. For example, if additional hard disks are added to a VM, an additional data vVol is created for each hard disk. Another example is when a snapshot is taken of a VM, and a new data vVol is created to store the snapshot. If the VM is powered on and its memory is also included in the snapshot, a memory vVol is created to store the contents of the VM’s memory. As additional vVols are created, the Virtual Volumes page in Unisphere is updated with the latest information.