VMware: Amount of Free Space Reported on The Host is Incorrect in vCenter Server

<< Symptoms >>

• In a VMware vSphere 4.1 Update 1 or newer environment, the Datastores view and the Summary tab in vCenter Server report an incorrect amount of free space on the host. 
• In a direct vSphere Client connection to an ESXi/ESX host, the values may be reported correctly if you manually refresh.
• Even after a manual refresh, the values may eventually be shown incorrectly.

<< Cause >>
The design of the vCenter Server environment in vSphere 4.1 Update 1 and later may show freespace of datastores in various resource windows which are out of sync from the actual value on the host for a period of five minutes. The vpxa agent on each host schedules a thread to monitor the free space on the datastore every five minutes; if the change in value is greater than 100 MB, it re-syncs this value on the vCenter Server.

<< Resolution >>
This is a known issue. This behavior is by design.

To work around this issue, use one of these methods:

Refresh the data using a PowerCLI Script
Execute a PowerCLI script which invokes the Get-Datastore -Refresh command on an hourly schedule to the host.

This is an example of running this command from the PowerCLI command line:

C:\Program Files\VMware\Infrastructure\vSphere PowerCLI> Get-Datastore -Refresh

Name         FreeSpaceMB    CapacityMB
----         -----------    ----------
isos         138986         554355
datastore1   2438           236544
MSCS-share   3298           3584
LH-iSCSI-0   15660          102144
LH-iSCSI-1   16612          50944

Change the refresh interval
To change the refresh interval, edit the configuration file and change the refreshInterval value to the desired interval.

To change the refreshInterval value:
1.  Using a text editor, open the /etc/vmware/hostd/config.xml file on the host.
2.  Locate the <datastore> element. This element in the default file is similar to:

<datastore>
   <!-- default datastore inventory-->
   <!-- <inventory>/etc/vmware/hostd/datastores.xml</inventory> -->
   <!-- default datastore refresh interval in minutes -->
   <!-- use 0 to disable the auto refresh -->
   <!-- <refreshInterval>0</refreshInterval> -->
   <!-- default datastore list refetch interval, after getting a VMFS event, in seconds-->
   <!-- <refetchVMFSDatastoreListInterval>30</refetchVMFSDatastoreListInterval> -->
</datastore>

3.  Remove the comment indicators and replace the 0 (zero) in the <refreshInterval> element with the desired number of minutes. For example, to set the refresh interval to one hour, change this line:

<!-- <refreshInterval>0</refreshInterval> -->
to:
<refreshInterval>60</refreshInterval>

4.  Save and close the file.
5.  Restart the host for the changes to take effect.


Reference:
Amount of free space reported on the host is incorrect in vCenter Server (2008367)
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2008367