VMFS5/6 datastores show 0B after host returned from reboot

Products

• VMware vSphere ESXi

Issue/Introduction

The following symptoms are observed in the vSphere Client and ESXi CLI:

• A specific datastore (e.g., ISOs) is visible in the vSphere Client UI but reports 0 Bytes for both Capacity and Free Space.

• An attempt to open the Datastore Browser yields the UI error: An error occurred, please try again.

• Standard HBA or standard storage rescans do not resolve the visibility issue.

• In an SSH/shell session, an inspection of /vmfs/volumes/ shows the datastore UUID or alias is missing.

• Execution of the esxcli storage filesystem list command shows the datastore is present on the storage fabric but the Mounted flag is set to false.
  [root@#########:~] esxcli storage filesystem list
Mount Point  Volume Name  UUID                                 Mounted  Type    Size  Free
-----------  -----------  -----------------------------------  -------  ------  ----  ----
             ####         ########-####-####-####-############    false  VMFS-6     0     0

Environment

ESXi 7.0.x

ESXi 8.0.x

Cause

This issue occurs because the VMFS datastore was previously administratively unmounted. ESXi explicitly preserves unmount states persistently across reboots and rescans to ensure safe storage fabric management.

Because the volume lacks an active mount point mapping in the /vmfs/volumes/ namespace, the ESXi storage daemon (hostd) cannot read the VMFS metadata. This missing metadata translation causes the UI to default to a 0-byte capacity and trigger a backend timeout or generic error when the Datastore Browser attempts to query the file system.

Following is logged in the hostd log after a rescan is performed:
####-##-##T##:##:## info hostd[#######] [Originator@####### sub=Libs opID=esxcli-##-#### user=svcvc] GetUnmountedVmfsFileSystemsInt: Found 14 unmounted VMFS volumes

Resolution

To resolve this issue, the datastore must be explicitly remounted. This can be accomplished via the vSphere Client GUI or the ESXi CLI.

Option A: Remount via vSphere Client (GUI)

1. Log in to the vSphere Client or the direct ESXi Host Client.

2. Navigate to the Storage view.

3. Select the affected host, then select the Datastores tab.

4. Locate the datastore reporting 0 bytes.

5. Right-click the datastore and select Mount Datastore.

6. Select the applicable hosts and confirm the operation.

Option B: Remount via ESXi CLI

1. Open an SSH session to the affected ESXi host.

2. Mount the datastore using its Volume Label:

   esxcli storage filesystem mount -l DatastoreName
   

   Alternatively, mount using the datastore UUID:

   esxcli storage filesystem mount -u ########-####-####-####-############