1. Introduction VMware Virtual Machine File System (VMFS) is a high-performance clustered file system designed for storing virtual machine disks (VMDKs), configuration files, and snapshots. Despite its robustness, VMFS volumes can become corrupted due to abrupt power loss, improper VMFS upgrades, faulty storage hardware, accidental formatting, or metadata corruption.
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: vmfs recovery
| 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 | 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: Step-by-Step Recovery Workflow 4
Example (pseudo‑script logic):
fd = read_fd(fd_number) for each block_pointer in fd.fbt: dd if=vmfs_disk.dd of=recovered_flat.vmdk \ bs=<vmfs_block_size> skip=<block_pointer> count=1 seek=<output_offset> These are stored in metadata heaps. Use vmfs-fuse (from vmfs-tools) in read‑only mode if superblock is partially valid: