An architect is designing a vSAN Original Storage Architecture (OSA) cluster for a VMware Cloud...

The extended resync behavior is best explained by deduplication and compression in a vSAN OSA design. In vSAN OSA, deduplication and compression are enabled at the cluster level but applied on a disk-group basis. The documentation states that deduplication occurs inline when data is written back from the cache tier to the capacity tier, and compression is then applied as data moves from cache to capacity. During resynchronization, vSAN must read, rewrite, deduplicate, compress, and destage data through this disk-group architecture. That additional processing can extend resync duration even when the physical network and hardware are healthy. “Ensure Accessibility” does not trigger a full component migration; it evacuates only enough data to maintain object accessibility and may leave objects temporarily noncompliant. The number of disk groups is not inherently the cause, and NVMe cache devices are not automatically limiting throughput simply because they are used in the cache tier. The key differentiator in the scenario is that deduplication and compression are enabled while heavy resync activity is occurring. Reference topics: vSAN OSA Deduplication and Compression, Disk Group Scope, Cache-to-Capacity Destaging, Maintenance Mode, Resynchronization.