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QNAP TS-453A 2 Out of the 4 Drives Failure

Data Recovery from Failed QNAP NAS RAID 5 Array with Multiple Disk Failures

Client Scenario

This case study involves a 4-bay QNAP TS-453A Network Attached Storage (NAS) system configured with four 6TB Western Digital Enterprise hard drives in a RAID 5 architecture. The client experienced a sudden complete system outage, during which the QNAP NAS became unreachable across the network. System shows that two out of the four drives had failed.

Client Profile & Challenge

  • Device: QNAP NAS TS-453A (4-Bay)
  • Storage Configuration: RAID 5
  • Media Type: 4 x 3.5" WD 6TB HDDs (Model: WD6002FFWX-68TZ4N0 & WD6003FFBX-68MU3N0)
  • The Crisis: Standard RAID 5 arrays can only tolerate the failure of a single drive. When two drives fail concurrently, parity protection breaks down completely, rendering the QNAP volume unmountable and causing a critical system offline error.

Technical Assessment Result

  • HDD 1 (Slot 1): Health Condition 0%
  • HDD 2 (Slot 2): Abnormal clicking sounds indicating head assembly mechanical damage.
  • HDD 3 (Slot 3): Fully functional.
  • HDD 4 (Slot 4): Fully functional.

The Technical Challenge: Since HDD 1 was totally dead (0%) and HDD 2 had mechanical head damage, we needed to stabilize both drives. Build up 2 sets of 3 readable drives (HDD 1/HDD 2 + HDD 3 + HDD 4). In RAID 5, 3 valid member drives are required to reconstruct the data block.

The Recovery Methodology

Phase 1: Hardware Cleanroom Servicing & Imaging

To prevent further media deterioration, recovery was performed on each individual drive. (Without powering on the NAS.)
  • Cleanroom Physical Repair (HDD 1 & 2): HDD 1 & 2 were safely opened to address the clicking issue. Recovery specialist replaced the faulty mechanical Head Stack Assembly (HSA) using matching donor components.
  • Sector-by-Sector Cloning: Once stabilized, HDD 1, 2, 3, and 4 were individually connected to professional hardware imager workstations. Using strict read-only hardware write-blockers, 1-to-1 clone images were extracted onto clean laboratory storage, capturing maximum raw sectors despite read errors on HDD 2.

Phase 2: Virtual RAID 5 Reconstruction

Because multi-drive NAS structures stripe files across all physical disks, file recovery cannot be performed by simply scanning single-member drives.
  • Analyzing: Recovery engineers analyzed the RAID metadata structures from the disk images to calculate the exact drive order, stripe block size, and parity distribution layout.
  • Degraded Virtual Array Mounting: With HDD 3 and HDD 4 at 100% and HDD 2's image successfully cloned, engineers virtually assembled the 3-disk RAID 5 array in a degraded state.

Phase 3: Volume Parsing & File Integrity Verification

Once the virtual array was bound and mounted in an isolated virtual sandbox:
  • EXT4/QTS File System Mapping: We mounted the native QNAP ext4/QTS storage volume, parsing the file allocation tables, directory inodes, and metadata maps.
  • File Extraction: Technicians systematically extracted all file structures.
  • Quality & Hash Auditing: Random sample multimedia and document files were audited to ensure full playback capabilities and header integrity without corruption or torn stripes.

Results & Data Extraction

We managed to recover all of the files with the original folder and path. The client checked all the recovered data, and the required data is all available. The client got a new drive and re-set up the NAS. Data is then transferred back into a healthy NAS.

Key Issue & Conclusions

Attempting a forced RAID rebuild when multiple drives exhibit hardware faults or abnormal clicking sounds will cause catastrophic head-to-platter contact, permanently scraping away data sectors.

Prompt professional data recovery centre's intervention may have higher chances of recovery. Feel free to contact us for further advice.

EHDR, We Leave No Data Behind.