VMware vSphere SDKs and Tools 8.0

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How Virtual Machines Access Storage

A virtual disk hides the physical storage layer from the virtual machine's operating system.
Regardless of the type of storage device that your host uses, the virtual disk always appears to the virtual machine as a mounted virtual storage device. As a result, you can run operating systems that are not certified for specific storage equipment, such as SAN, in the virtual machine.
When a virtual machine communicates with its virtual disk stored on a datastore, it issues virtual device interface commands appropriate for the device. Because datastores can exist on various types of physical storage, these commands are encapsulated into other forms, depending on the protocol that the
ESXi
 host uses to connect to a storage device.
Figure 1 depicts five virtual machines that use different types of storage to illustrate the differences between each type.
Virtual Machines Accessing Different Types of Storage
Displays relations between virtual machines and different types of storage. The objects are grouped by type and there are lines that connect them.
You can use ESXCLI commands to manage the virtual machine file system and storage devices.
  • Datastores - Several commands allow you to manage datastores and are useful for multiple protocols.
    • LUNs - Use
      esxcli storage core
       to display available LUNs and mappings for each VMFS volume to its corresponding partition. See Examining LUNs.
    • Path management - Use
      esxcli storage core
       to list information about Fibre Channel or iSCSI LUNs and to change a path’s state. See Managing Paths. Use the ESXCLI command to view and modify path policies. See Managing Path Policies.
    • Rescan - Use
      esxcli storage core
       to perform a rescan operation each time you reconfigure your storage setup. See Scanning Storage Adapters.
  • Storage devices - Several commands manage only specific storage devices.
  • Software-defined storage - vSphere supports several types of software-defined storage.
    • vSAN
       storage - Use commands in the
      esxcli vsan
       namespace to manage
      vSAN
      . See Monitoring and Managing vSAN Storage.
    • Virtual Flash storage - Use commands in the
      esxcli storage vflash
       namespace to manage VMware vSphere Flash Read Cache.
    • Virtual volumes - Virtual volumes offer a different layer of abstraction than datastores. As a result, finer-grained management is possible. Use commands in the
      esxcli storage vvol
       namespace.

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