What happens when a datastore runs out of space?
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When a datastore runs out of space, thin-provisioned virtual disks can no longer dynamically grow to accommodate additional storage demand. When VMware ESX detects this condition, virtual machines in need of additional storage are instantly paused to prevent guest operating systems from failing.
How can I increase disk space in datastore?
Navigate to Storage > Datastores and select the datastore you are trying to expand or increase. Right-click on the datastore and select Increase Capacity. Alternatively, select the Increase capacity button.
What will happen if datastore is full?
If the VMFS is unable to accommodate the additional data, the snapshot does not grow, does not get written, or is not committed. As a result, the virtual machine may fail. File copy, ls commands and a variety of Linux-level functions perform poorly when the space is full because the VMware VMFS is a filesystem.

What can we add to a VMFS datastore to grow its capacity?
How to Increase VMFS Datastore Capacity VMware vSphere
- Login VMware vSphere Client, using username and password.
- Select Storage icon.
- Select your datastore the one you want to increase the size, Select Action menu, and then click Increase Datastore Capacity.
Can we reduce disk size in VMware?

In Windows: Double-click the VMware Tools icon in the system tray, or click Start > Control Panel > VMware Tools. Note: In Workstation 9. x (Windows) and later, shrinking is automatically done while cleaning up the disk.
What is space reclamation?
In a thinly provisioned environment, space reclamation completes the process of freeing space from the storage system that has been freed in the host file system.
What is Datastore usage on disk?
Datastore usage on disk alarms can be used to monitor the percentage of disk space usewd on each datastore in your vSphere environment. The default settings of the Datastore usage on disk alarm is to trigger a Warning when disk usage exceeds 75% and an Alert at 85%.