vsanDatastore appears as 0 bytes in size following cluster membership changes
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vsanDatastore appears as 0 bytes in size following cluster membership changes

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Article ID: 326421

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Updated On:

Products

VMware vSAN

Issue/Introduction

This article details the cause and solution to one of the reasons a vSAN cluster's datastore may appear as 0 bytes, when checked via the vSphere client or CLI.

Symptoms:
vSAN datastore appears as 0 B in size in the vSphere client but appears as normal size when checked from host Client or via SSH.

Environment

VMware vSAN 6.x
VMware vSAN 7.0.x
VMware vSAN 8.0.x

Cause

Hosts improperly added to or removed from a vSAN cluster can have vSAN enabled while they have no network access between all other hosts in the same cluster - from these hosts' perspective the vSAN datastore is 0B in size.

vSAN is a distributed storage system and each host connects with all other hosts to establish and build up the vSAN datastore. If one host is isolated from the rest of the cluster, it cannot bring the vSAN datastore on this specific host online and not contribute or consume any space.

vCenter uses random hosts to query datastores for its utilization, as vCenter does not have direct access to the underlying storage. Hence when vCenter chooses the isolated hosts, it will display the wrong size.

Resolution

Identify any hosts that have been improperly added to or removed from the cluster that still have vSAN enabled but with no network connection to the other cluster members.

These can be identified via the vSphere client and validating that only the hosts that are part of the current vSAN cluster and have vSAN network configured appear here: Datastores > vsanDatastore > Hosts

If extraneous hosts that should not or do not have access to the datastore are listed then these still have vSAN enabled, this can be disabled via SSH to the host:
# esxcli vsan cluster leave

If you are unsure about making changes, please make changes during maintenance windows, if possible, or do consult VMware Support with the respective severity. Leaving hosts or changing the membership list can cause cluster partition and objects to go inaccessible.

Additional Information

Note that there can be other causes of vsanDatastore appearing as 0 bytes, including cluster member(s) being network partitioned 

Impact/Risks:
Provisioning of vSAN Objects (e.g. VMDK, snapshots, namespaces) may fail if the vSAN datastore appears as 0B in size.