Space issues on vSAN do not allow a storage policy change.
Article ID: 392223
Updated On:
Products
Issue/Introduction
Space can sometimes be taken up unexpectedly. Sometimes there are forgotten snapshots, unexpected VM growth, and unassociated objects. Unassociated objects are vSAN objects but are not associated with an active VM in the VC inventory.
Environment
VMware vSAN (All Versions)
Cause
In vSAN, it is recommended to keep a minimum amount of available space on the datastore. One should maintain 25-30% slack space when designing and running a vSAN cluster. For example, a vSAN datastore with 20TB of raw capacity should always have 5-6TB of free space available for use as slack space. When this is not maintained, trying to convert a large VM from a RAID-1 storage policy to say RAID-5 may not work. The two object sets for the VM will be active concurrently as the RAID conversion progresses. Thus, there must be available space for both object sets during the conversion.
Resolution
If already in a limited space situation, the best resolution is to add additional capacity to the vSAN environment either by adding more disks to the existing servers if empty disk back are available or by adding more hosts to the cluster. Unnecessary VMs or user files might also be removed or migrated off of the vSAN. During the object re-layout there might be a slight performance hit to the VM. Typically this is a low-priority background task and thus can be done any time. However, it is recommended to do the storage policy conversion under lower workload or after hours.
In some cases there may be unassociated objects that are no longer in use. These can be deleted to return used space, but care must be taken to verify each object. Unassociated does not always mean not used. KB with more info below.
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