Let’s say you have a Windows Server running as a virtual machine on ESXi. Let’s also say it’s disks ran out of free space.
To add more storage to this virtual machine, first we’ll need to extend the volume it’s running from. In my case this VM is running off of a Equallogic SAN.
Start the Equallogic Group Manager, and locate the volume on which the VM lives.
Right click on it and select Modify Settings.
In the Modify volume settings window, click on the Space tab, then in the Volume Size field enter the desired volume size. Click on the OK button.
At the next prompt, select Yes to create a snapshot prior to extending the volume. Give the snapshot a description and click on OK.
Note that the size of the volume has changed now, including the amount of free space.
Next we’ll need start the vSphere client and connect to the vCenter instance. Select the host, then click on the Configuration tab then Storage on the left hand side.
Select the Datastore you need to add space to.
Right click on it and select Properties.
Click on the Increase button.
Select the LUN to expand the Datastore, then click on Finish.
Back in the vSphere client, select the VM that we are adding space to, then right click on it, and select Edit Settings.
Select the Virtual Disk you want to add space to and enter in the new value in the Provisioned Size field.
Now let’s go back to the Windows Server virtual machine. In it, let’s start Server Manager, and then go to start Disk Management.
In the menu bar click on Action, and select Rescan Disks from the menu.
Now you’ll see (new) unallocated space show up.
Right click on the disk partition you want to add space to, and select Extend Volume.
Select the disk with the unallocated space and specify the amount of space you want to use to extend the other disk partition.
Notice that the Size of the Disk 1 increased from 220GB to 310GB.
And voila we have some free space available to work with.