A vSAN administrator has recently upgraded a vSAN cluster to 8.

The Capacity Reserve feature in vSAN 8.0 OSA reduces the amount of capacity reserved for transient and rebuild operations by using a slack space threshold. This threshold is calculated based on the size of the largest component in the cluster and the number of failures to tolerate. If the used space on vSAN datastore exceeds the suggested slack space threshold, the feature will not operate properly and vSAN will revert to using the host rebuild reserve threshold. The other scenarios will not affect the Capacity Reserve feature. References: [VMware vSAN Specialist v2 EXAM 5V0-22.23], page 28