Multiple Datastores in vCenter report a Status as Unknown

Products

VMware vCenter Server VMware vSphere ESXi

Issue/Introduction

The Storage Status section in vCenter Server shows a status of "Unknown" (Gray Icon) rather then "Normal".
For example:
- This issue may originally occur with specific datastores, but may eventually affect all datastores.
- Newly created datastores, show as unknown but while pre-existing datastores show as "Normal" (Green Icon).
- The storage status may display as "Unknown" for all datastores, or only for a specific subset of individual datastores.
Functionality remains unaffected, and storage hardware reports healthy.

Environment

VMware vCenter Server 8.0.3
VMware vSphere ESXi 8.0.3

Cause

Cause: This issue occurs for the following reasons:

Metric Inheritance Break: Moving the alarm definition to a specific Datacenter prevents newly created Datacenters or Datastores from inheriting the alarm, causing them to default to "Unknown."
Disabled/Missing Alarm: The "Datastore usage on disk" alarm is disabled, deleted, or overridden at the vCenter, Datacenter, or Datastore level. This alarm drives the UI storage status metric.
State Persistence: If an alarm is deleted after it has already evaluated a datastore as "Normal," the vSphere Client may continue to display the cached "Normal" status. The status will only update to "Unknown" once the vpxd service is restarted or a fresh evaluation is forced.

Resolution

The Storage Status is reported by the Datastore usage on disk alarm, which monitors datastore disk usage. This is a preconfigured alarm and it triggers automatically when problems are detected. This issue may occur if you have disabled the action for this alarm.

Step 1: Verify the alarm at the vCenter Server Level

Select the vCenter Server object at the top of the inventory.
Navigate to Configure > Alarm Definitions.
Search for the alarm named "Datastore usage on disk".
Verify if the alarm is Enabled. If disabled, click Enable.
If the alarm is missing, recreate the default alarm at the vCenter root level.

Step 2: Verify the alarm at the specific Datastore Level: If the global alarm is enabled, but specific datastores still display an "Unknown" status, the alarm may be overridden locally:

Select the Storage inventory view in the vSphere Client.
Select the specific datastore that displays the "Unknown" status.
Navigate to Configure > Alarm Definitions.
Search for the alarm named "Datastore usage on disk".
Verify if the alarm is Enabled. If the alarm is explicitly disabled at this object level, select it and click Enable to reactivate the metric collection.
Repeat this process for any other datastores displaying an "Unknown" status.

Step 3: Clear Stale Status (Optional):

If the alarm is enabled but the status remains "Unknown" (or if you need to verify if "Normal" is a cached state), restart the vCenter services.
For steps on restarting services, see Stopping, starting, or restarting VMware vCenter Server services.

Note: If your problem still exists after trying the steps in this article, file a support request with VMware Support and note this Knowledge Base article ID (vCenter Server Storage Status displays as Unknown) in the problem description. For more information, see How to Submit a Support Request.

Additional Information

A "Normal" (Green) status indicates the alarm logic is active and thresholds are not met.
An "Unknown" (Gray) status indicates the alarm logic is not being evaluated for that object.
When an object is selected in the Inventory, you can identify its disabled alarm actions:
- In the General pane of the object's Summary tab.
- In the Alarm Actions Disabled pane of the Alarms tab.
- In the Alarm Actions column of the object's child object tabs. For example, if you select a host in the inventory, the Virtual Machines tab displays whether alarm actions are enabled or disabled for each virtual machine on the host.
The alarm for datastore disk usage is enabled at the datacenter level.