Introduction VMware Virtual Machine File System (VMFS) is the backbone of vSphere environments, designed for high-performance concurrent access by multiple ESXi hosts. Despite its robustness, VMFS is not immune to corruption. Among the most dreaded scenarios for a storage administrator is the loss or corruption of VMFS metadata—the critical set of structures that tells the hypervisor where files (virtual disks, configurations, snapshots) reside on the underlying LUN or disk device.
# Find backup superblock locations (example for VMFS6) # Primary at LBA 1, backup at LBA 2048, 4096, etc. dd if=/vmfs/devices/disks/naa.6000... of=/tmp/backup_superblock bs=512 count=1 skip=2048 # Restore primary dd if=/tmp/backup_superblock of=/vmfs/devices/disks/naa.6000... bs=512 count=1 seek=1 Incorrect offsets can destroy data. Only attempt if you have exact documentation for your VMFS version. 3.3 Third-Party Recovery Tools (Recommended for Critical Data) Several commercial tools specialize in VMFS metadata reconstruction. They work by scanning the raw device for file signatures and rebuilding the allocation map.
Without valid metadata, a datastore appears as a raw partition, empty, or reports the dreaded "Not a VMFS datastore" error. However, the actual virtual machine data (VMDK files, memory state, logs) often remains physically present on the disk. Recovering the metadata is therefore less about file “undelete” and more about reconstructing the logical map that points to existing data blocks. recover vmfs metadata
vmfs-fs-rescue /vmfs/devices/disks/naa.6000...:1 This creates a lost+found directory with recoverable files. It does not preserve original folder structure but may recover VMDK and VMX files. VMFS does not have an fsck like ext4. Instead, VMware relies on journal replay on mount. To force replay:
# List all partitions on a device (e.g., naa.6000...) partedUtil get /vmfs/devices/disks/naa.6000... fdisk -l /vmfs/devices/disks/naa.6000... Attempt to probe filesystem vmfs-fs-probe /vmfs/devices/disks/naa.6000...:1 View kernel VMFS errors tail -100 /var/log/vmkernel.log | grep -i vmfs Introduction VMware Virtual Machine File System (VMFS) is
dd if=/vmfs/devices/disks/naa.6000... bs=512 count=1 | hexdump -C Look for “VMFS” ASCII signature at offset 0x200. If present but higher-level structures corrupt, recovery is possible. Recovery options depend on whether you have backups, ESXi’s built-in repair utilities, or need third-party tools. 3.1 First Line: ESXi Built-in Commands A. vmfs-fs-rescue (VMFS3/5 only – deprecated in newer versions) For older environments, this utility attempts to rebuild the FDC table from residual metadata.
esxcfg-volume -l # List snapshot volumes esxcfg-volume -r <vol_name> # Resignature (keeps data) VMFS6 stores redundant copies of critical metadata structures. You can manually copy a backup superblock: # Find backup superblock locations (example for VMFS6)
# Unmount if mounted vmkfstools -V /vmfs/devices/disks/naa.6000...:1 # Remount to replay journal esxcfg-volume -M <datastore_name> If corruption is due to ESXi detecting a duplicate UUID, resignaturing preserves metadata but changes datastore identity: