Using these tools is a fundamentally different process: one must present the raw LUN to a Windows or Linux workstation, run the recovery tool in read-only mode, and export recovered files (usually flat VMDKs or configuration files) to a new , healthy datastore. This is not a "repair" of the original datastore but a rescue operation. It is time-consuming (often days for multi-terabyte volumes) and requires sufficient staging space. Success depends entirely on the degree of fragmentation and whether the corruption has destroyed the VMFS heartbeat region. Ultimately, the most profound insight about repairing a VMFS datastore is that a successful repair is a failure of planning. In enterprise environments, the correct response to a corrupted datastore should be deletion and restoration from backup or storage-level snapshot, not online repair. The time spent running vmkfstools -F on a 10 TB datastore could exceed the RTO (Recovery Time Objective) of most critical applications.
For more severe cases—where the VMFS volume is unmountable—the esxcli storage vmfs command family offers esxcli storage vmfs snapshot mount and esxcli storage vmfs resignature . Resignaturing is a critical technique used when a datastore’s UUID conflicts with another (e.g., after a snapshot restore). It generates a new UUID, allowing the datastore to mount, but it breaks any snapshot chains or replicas dependent on the old signature. This is a "repair" of availability, not integrity. When native tools fail—typically in cases of overwritten metadata blocks or severe disk-level corruption—the administrator must turn to specialized third-party utilities. Tools like UFS Explorer RAID Recovery (which includes VMFS parsers), Runtime Software's GetDataBack for VMFS , or Stellar Data Recovery for VMware can scan raw block devices to reconstruct the VMFS structure. These tools operate by recognizing VMFS file signatures (e.g., the fdc.db file for descriptor chains) and ignoring the corrupt filesystem layer. repair vmfs datastore
The first rule of repair is diagnostic rigor. An administrator must connect to each ESXi host via SSH or the DCUI and run esxcfg-scsidevs -m to see if the device is detected at the physical layer, then vim-cmd hostsvc/storage/query to assess logical visibility. Often, the problem is not corruption but a "stale lock"—a remnant from a host that lost communication but never released its reservation. In such cases, the repair is a simple, non-destructive vmkfstools -D to check lock status, followed by releasing orphaned locks. VMware provides a surprisingly powerful yet underutilized command-line toolkit for datastore repair, primarily vmkfstools and esxcli storage filesystem . The most famous command in this domain is vmkfstools –fix , which performs a filesystem consistency check (FSCK) specific to VMFS. Using these tools is a fundamentally different process:
The vmkfstools -F (or --fix ) switch is the closest analogue to Windows chkdsk . When executed against a volume path (e.g., vmkfstools -F check /vmfs/volumes/DatastoreName ), it scans for metadata inconsistencies, orphaned file descriptors, and incorrect resource counts. However, this is not a magic wand. It operates in three phases: "check" (read-only), "repair" (fixing minor issues like incorrect link counts), and "fix" (attempting more aggressive recovery). A crucial caveat: vmkfstools cannot recover actual file data; it can only repair the filesystem's pointers. If a virtual machine's VMDK descriptor file points to the wrong blocks, the repair may succeed logically while leaving the VM booting to a blue screen. Success depends entirely on the degree of fragmentation