You can use thin provisioned storage arrays with ESXi.

Traditional LUNs that arrays present to the ESXi host, are thick-provisioned. The entire physical space needed to back each LUN is allocated in advance.

ESXi also supports thin-provisioned LUNs. When a LUN is thin-provisioned, the storage array reports the LUN's logical size, which might be larger than the real physical capacity backing that LUN.

A VMFS datastore that you deploy on the thin-provisioned LUN can detect only the logical size of the LUN. For example, if the array reports 2TB of storage while in reality the array provides only 1TB, the datastore considers 2TB to be the LUN's size. As the datastore grows, it cannot determine whether the actual amount of physical space is still sufficient for its needs.

However, when you use the Storage APIs - Array Integration, the host can integrate with physical storage and become aware of underlying thin-provisioned LUNs and their space usage.

Using thin provision integration, your host can perform these tasks:

  • Monitor the use of space on thin-provisioned LUNs to avoid running out of physical space. As your datastore grows or if you use Storage vMotion to migrate virtual machines to a thin-provisioned LUN, the host communicates with the LUN and warns you about breaches in physical space and about out-of-space conditions.
  • Inform the array about the datastore space that is freed when files are deleted or removed from the datastore by Storage vMotion. The array can then reclaim the freed blocks of space.
Note: ESXi does not support enabling and disabling of thin provisioning on a storage device.


To use the thin provision reporting feature, your host and storage array must meet the following requirements:

  • ESXi version 5.0 or later.
  • Storage array has appropriate firmware that supports T10-based Storage APIs - Array Integration (Thin Provisioning). For information, contact your storage provider and check the HCL.