dcfldd if=/dev/sdX of=vmfs_disk.dd hash=sha256 hashlog=hash.txt bs=1M conv=noerror,sync # Or using ddrescue for failing drives ddrescue -f /dev/sdX vmfs_disk.dd vmfs_mapfile Commercial tools are often the fastest path:
: Never trust a single VMFS datastore – replication and backups remain the only guaranteed recovery path. This write-up is for authorized forensic analysis and disaster recovery only. Always comply with software licensing and data privacy laws. vmfs recovery
dd if=vmfs_disk.dd bs=512 | strings -n 8 | grep -E "FD.4,8VMFS" Manually map FD number → block pointers. If you have the FD for a flat VMDK ( -flat.vmdk ), you can extract its data blocks sequentially using the FB table. dcfldd if=/dev/sdX of=vmfs_disk
| Structure | Purpose | Location (LBA offset) | |-----------|---------|------------------------| | | FS UUID, version, block size, heartbeat region | LBA 128 (VMFS5/6), LBA 1 (VMFS3) | | File Descriptor (FD) | Inode-like entry pointing to FB/PC regions | Varies – part of file system heap | | FBC (File Block Map) | Physical block pointers for file data | Allocated from metadata heap | | Heartbeat Region | LUN ownership & cluster health | LBA 0x1000 – 0x2000 | | Resource Allocation (RA) | Free block tracking | Located in metadata partition | | Directory Entries (DirEntry) | Filename ↔ FD mapping | Inside .vmdk directory or root | Recovery principle : If superblock is intact, the FS can be logically remounted. If not, you must scan for FDs and rebuild the block map. 4. Step-by-Step Recovery Workflow 4.1 Initial Assessment (Non‑destructive) # Identify VMFS partitions (Linux with vmfs-tools or esxcli) esxcli storage vmfs snapshot list partedUtil get /dev/disks/naa.600... | grep vmfs Check if superblock is readable dd if=/dev/sdX bs=512 skip=128 count=1 | hexdump -C | head -20 Look for magic string "VMFS" or "VMFS5"/"VMFS6" 4.2 Full Disk Imaging (Mandatory) Always work on a forensic image to preserve evidence: dd if=vmfs_disk
| Tool | Best for | |------|----------| | | VMFS3/5/6, deleted VMDKs, RAID reconstruction | | R‑Studio | VMFS datastores with partition table loss | | SysTools VMFS Recovery | Simple file extraction from healthy metadata | | vmfs-tools (open source) | Manual CLI recovery, limited to clean FS |
vmfs-fuse -o ro /dev/loop0 /mnt/recovery If that fails, carve small files by known headers ( #! for VMX, KDMV for VMDK descriptor). Situation : An administrator ran vmkfstools -C vmfs5 /dev/disks/... on a datastore containing 12 production VMs.