Error: vSAN optimal datastore default policy configuration in ESA cluster.
Article ID: 444255
Updated On:
Products
Issue/Introduction
From Cluster > Monitor > vSAN > Skyline Health there is an alarm for "VSAN Optimal Datatsore Default Policy Configuration"
The health check suggests changing the policy from RAID-5 (Erasure Coding) to RAID-1 (Mirroring).
Disabling Host Rebuild Reserve clears the alarm, but re-enabling it triggers the warning again.
Environment
VMware vSAN ESA 8.x
Cause
The alarm is triggered by the interaction between Auto-Policy Management and Host Rebuild Reserve (HRR).
The following table illustrates the "Optimal Policy" determined by Auto-Policy Management when Host Rebuild Reserve is enabled and Host Rebuild Reserve turned off.
When HRR is Enabled.
| Host Count | Optimal Policy (ESA) |
| 3 Nodes | HRR is not supported |
| 4 Nodes | RAID-1 (Mirroring) |
| 5 Nodes | RAID-5 (2+1) |
| 6 Nodes | RAID-5 (4+1) |
| 7 Nodes | RAID-6 (4+2) |
When HRR is Not Enabled.
Host Count | Optimal policy (ESA) |
3 Nodes | RAID-1 (Mirroring) |
4 Nodes | RAID - 5 (2+1) |
5 Nodes | RAID - 5 (2+1) |
6 Nodes | RAID - 6 (4+2) |
For example, In a 4-node ESA cluster, enabling HRR reserves the capacity of one full host for rebuilds. This leaves only three active hosts available for data placement. Since RAID-5 (2+1) requires at least three active hosts to function, the cluster would have no remaining overhead to automatically restore full redundancyif a host fails.
Therefore, vSAN identifies RAID-1 (Mirroring) as the only "optimal" policy that can maintain automatic compliance within the reserved resource constraints.
Resolution
To resolve the health warning, choose one of the following three options based on requirements:
Option 1: Acknowledge and Silence the Alert If RAID-5 capacity efficiency is required and manual rebuild management during a host failure is accepted:
Navigate to the vSphere Client.
Select the vSAN Cluster.
Go to Monitor > vSAN > Skyline Health.
Locate and select the vSAN optimal datastore default policy configuration health check.
Click Silence Alert.
Option 2: Align with Optimal Policy Recommendation Change the vSAN default storage policy to RAID-1 to ensure automatic rebuild compliance.
Navigate to Policies and Profiles > VM Storage Policies.
Edit the active vSAN Default Storage Policy.
Change the Failures to Tolerate rule to 1 failure - RAID-1 (Mirroring).
Apply the policy to the datastore.
Option 3: Scale the Cluster - Add another host to the cluster. This provides sufficient active node overhead to support RAID-5 (2+1) while maintaining a full Host Rebuild Reserve.
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