6.7

Handling Datastore Over-Subscription
Because the provisioned space for thin disks can be greater than the committed space, a datastore over-
subscription can occur, which results in the total provisioned space for the virtual machine disks on the
datastore being greater than the actual capacity.
Over-subscription can be possible because usually not all virtual machines with thin disks need the entire
provisioned datastore space simultaneously. However, if you want to avoid over-subscribing the
datastore, you can set up an alarm that notifies you when the provisioned space reaches a certain
threshold.
For information on setting alarms, see the vCenter Server and Host Management documentation.
If your virtual machines require more space, the datastore space is allocated on a first come first served
basis. When the datastore runs out of space, you can add more physical storage and increase the
datastore.
See Increase VMFS Datastore Capacity.
ESXi and Array Thin Provisioning
You can use thin-provisioned storage arrays with ESXi.
The ESXi host integrates with block-based storage and performs these tasks:
n
The host can recognize underlying thin-provisioned LUNs and monitor their space use to avoid
running out of physical space. The LUN space might change if, for example, your VMFS datastore
expands or if you use Storage vMotion to migrate virtual machines to the thin-provisioned LUN. The
host warns you about breaches in physical LUN space and about out-of-space conditions.
n
The host can run the automatic T10 unmap command from VMFS6 and VM guest operating systems
to reclaim unused space from the array. VMFS5 supports a manual space reclamation method.
Note ESXi does not support enabling and disabling of thin provisioning on a storage device.
Requirements
To use the thin provisioning reporting and space reclamation features, follow these requirements:
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Use an appropriate ESXi version.
Table 25‑1. ESXi Versions and Thin Provisioning Support
Supported thin provisioning components ESXi 6.0 and earlier ESXi 6.5 and later
Thin provisioning Yes Yes
Unmap command originating form VMFS Manual for VMFS5. Use
esxcli storage vmfs
unmap.
Automatic for VMFS6
Unmap command originating from guest OS Yes. Limited support. Yes (VMFS6)
vSphere Storage
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