These tools install a kernel-level filter driver that interprets VMFS structures and presents them as a disk device or a mounted folder. For write access, they must handle VMware’s distributed locking — a complex task. That’s why read/write tools are expensive and not open-source.
The fix didn’t happen all at once. Dante staged the recovery: repair, verify, mount read-only, verify again, then finally commit. When he remounted the VMFS in read-write mode, the datastore flickered back into life and the VM’s services answered pings. The Windows host cooled as its processes settled. Around him, operators exhaled.