This guide covers the process of recovering data from a degraded or failed RAID5 array using Linux data recovery tools and restoring the recovered data on a Synology NAS storage system.
Requirements
- Linux machine with mdadm, TestDisk, and ddrescue utilities installed
- Synology NAS on the same network as the Linux machine
- Enough disk space on the Linux machine to store the recovered RAID data
Steps
1. Stopping the RAID array
If the RAID5 array is still running, stop it first:
mdadm --stop /dev/mdX
This prevents further data loss.
2. Imaging the RAID disks
Attach the RAID5 member disks to the Linux machine using a disk interface like SATA/USB.
Image each disk sequentially using ddrescue to create full disk images:
ddrescue -f -n /dev/sdX /path/to/image.img /path/to/log.txt
This safely captures all recoverable data from the disks while minimizing stress.
3. Assembling the RAID in Linux
With the disk images captured, assemble the RAID5 array in Linux using mdadm:
mdadm --assemble --run /dev/mdX /path/to/disk1.img /path/to/disk2.img
Check dmesg and /proc/mdstat to ensure the array is running.
4. Mounting the RAID
Mount the assembled RAID5 array to begin data recovery:
mount /dev/mdX /mnt/raid-recover
5. Recovering files from the RAID
Use TestDisk to scan the mounted array and extract recoverable files:
testdisk /dev/mdX
Follow the interactive prompts to find deleted or lost partitions and recover files.
Alternative file recovery tools like PhotoRec can also be used.
6. Transferring the recovered data
Once file recovery is completed, transfer the extracted data to the Synology NAS:
rsync -avh /mnt/raid-recover/recovered/ /volume1/data
Verify that the data is now available on the NAS storage through file browsers.
This completes the RAID5 recovery on Linux and restoration on Synology NAS. The technical process leverages disk imaging, Linux MDADM, data recovery tools and network file transfer to successfully recover and restore data.
Key Concepts and Technologies:
RAID – Redundant Array of Independent Disks. RAID5 uses distributed parity and striping across member disks to provide fault tolerance and improve performance.
Linux mdadm – Linux tool for managing software RAID arrays including assembly, stopping, and recovery.
ddrescue – Linux data recovery tool that isolates readable data and minimizes disk stress. Better than dd for imaging damaged drives.
TestDisk – Data recovery utility designed to find lost partitions, fix boot issues, and undelete files.
Synology NAS – Network Attached Storage appliance from Synology providing RAID, shared storage and backups. More advanced than basic external HDDs.
Data Recovery Techniques
- Imaging – Safely duplicate disk contents to an image file without modifying source.
- Reassembly – Logically rebuild a failed RAID using images of member disks.
- File Carving – Scan disk images and extract files based on headers, magic numbers etc.
RAID5 Advantages
- Distributed parity provides redundancy against single disk failure.
- Striping improves performance over a single large disk.
- Cost effective compared to mirrors or parity of RAID6, RAID10.
Synology NAS Benefits
- Network access allows easy central backups and recovery.
- Advanced RAID configurations like SHR, Link Aggregation.
- Features like versioning, encryption, caching not in basic USB disks.
