vsphere-esxi-vcenter-server-55-storage-guide

Chapter 25 Storage Thin ProvisioningIf your virtual machines require more space, the datastore space is allocated on a first come first servedbasis. When the datastore runs out of space, you can add more physical storage and increase the datastore.See “Increase VMFS Datastore Capacity in the vSphere Web Client,” on page 144.Array Thin Provisioning and VMFS DatastoresYou can use thin provisioned storage arrays with ESXi.Traditional LUNs that arrays present to the ESXi host, are thick-provisioned. The entire physical spaceneeded to back each LUN is allocated in advance.ESXi also supports thin-provisioned LUNs. When a LUN is thin-provisioned, the storage array reports theLUN'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 datastoreconsiders 2TB to be the LUN's size. As the datastore grows, it cannot determine whether the actual amountof physical space is still sufficient for its needs.However, when you use the Storage APIs - Array Integration, the host can integrate with physical storageand 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 yourdatastore 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 outof-spaceconditions.• Inform the array about the datastore space that is freed when files are deleted or removed from thedatastore 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.RequirementsTo use the thin provision reporting feature, your host and storage array must meet the followingrequirements:• ESXi version 5.0 or later.• Storage array has appropriate firmware that supports T10-based Storage APIs - Array Integration (ThinProvisioning). For information, contact your storage provider and check the HCL.Space Usage MonitoringThe thin provision integration functionality helps you to monitor the space usage on thin-provisioned LUNsand to avoid running out of space.The following sample flow demonstrates how the ESXi host and the storage array interact to generatebreach of space and out-of-space warnings for a datastore with underlying thin-provisioned LUN. The samemechanism applies when you use Storage vMotion to migrate virtual machines to the thin-provisionedLUN.1 Using storage-specific tools, your storage administrator provisions a thin LUN and sets a soft thresholdlimit that, when reached, triggers an alert. This step is vendor-specific.2 Using the vSphere Web Client, you create a VMFS datastore on the thin-provisioned LUN. Thedatastore spans the entire logical size that the LUN reports.VMware, Inc. 249