In VMware Cloud Foundation 9.0 with vSAN ESA, storage policies must match the capabilities of the existing cluster. The scenario describes a5-node vSAN ESA clusterwhere the vSAN Default Storage Policy isRAID-1 (FTT=1). The administrator attempts to apply a2 Failures – RAID-6policy, which ESA supportsonly on clusters with at least 7 nodes. Because the cluster has only five nodes, the policy fails immediately—this is expected and documented in the vSAN ESA design specifications.

Since RAID-6 is not an option and capacity is low, the administrator must look for a method to reclaim storage usage without requiring additional nodes or unsupported policy changes. Converting VMs fromthick provisioning to thin provisioningis a safe and effective mitigation approach. Thin provisioning reduces consumed space by allowing disks to grow only as needed, immediately recovering unused blocks. This is a standard vSAN-supported method to temporarily alleviate capacity pressure.

Enabling encryption (A) or compression (D) doesnotreduce capacity usage retroactively and may actually increase overhead. Using RAID-5 (B) is also not possible because RAID-5 requiresat least 6 ESA-enabled hosts.