This write-up outlines a systematic methodology for recovering data from damaged or inaccessible VMFS datastores (VMFS3, VMFS5, VMFS6) using low-level disk analysis and specialized recovery tools. | Symptom | Possible Cause | |---------|----------------| | Datastore appears as "not mounted" or "unmounted" in vSphere | Corrupt heartbeats or partition table | | VMs missing from inventory but .vmx/.vmdk files visible via CLI | Lost directory entries or corrupt file descriptors (FDs) | | Unable to power on VM: "File system specific error" | Corrupt VMFS metadata (FB, PB, or resource allocation) | | Entire LUN shows as raw or snapshot LUN | Overwritten VMFS superblock or partition table | | Deleted VMDKs still consuming space | Orphaned file blocks without FD links | 3. VMFS Metadata Structures (Recovery Essentials) Understanding key on-disk structures is critical for manual recovery:
sgrep -b 'VMFS5' vmfs_disk.dd FDs start with a known pattern (e.g., FD 00 00 01 for VMFS5). Scan the entire disk:
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. vmfs recovery
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.
| 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 | Scan the entire disk: dd if=vmfs_disk
Example (pseudo‑script logic):
# Check VMDK descriptor consistency vmkfstools -Q recovered_vm.vmdk dd if=recovered_flat.vmdk bs=1M count=1 | hexdump -C Attempt to mount or clone vmkfstools -i recovered_flat.vmdk -d thin verified.vmdk Introduction VMware Virtual Machine File System (VMFS) is
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: