Many NAS devices utilize RAID (Redundant Array of Independent Disks) configurations to protect against data loss due to drive failure. When a drive in a RAID array fails, a “rebuild” process is initiated to restore redundancy by copying data to a new or spare drive.
A rebuild can allow for continuity, but there are situations where attempting a NAS rebuild can be risky. If you don’t have a backup of the data on the NAS, the safest course of action is to work with a professional data recovery provider.
We realize that we’re biased, but this isn’t an attempt to get easy business — the vast majority of our NAS data recovery cases involving RAID begin with a failed attempt at a rebuild. Those failures can make data recovery much more complicated and put data at risk.
Remember, redundancy is not backup: If your NAS contains the only copy of important data and it’s currently inaccessible, you’re dealing with a data recovery scenario. Take it seriously!
Datarecovery.com provides risk-free evaluations for NAS systems, along with a no data, no charge guarantee for data recovery cases. Submit a case online or call 1-800-237-4200 to learn more.
Below, we’ll explain some of the red flags that can indicate the need for professional assistance. Note that this is not a comprehensive list; any RAID rebuild can fail under the wrong circumstances.
Red Flags: When a NAS Cannot Be Safely Rebuilt
A rebuild puts extra stress on storage media, since the missing drive will need to be rebuilt from the parity data. That requires intensive operation of the remaining drives and pre-existing issues can be exacerbated.
Before initiating a rebuild, thoroughly assess the health of your NAS hardware:
- Drive Health: Pay close attention to SMART (Self-Monitoring, Analysis and Reporting Technology) data. A high number of reallocated sectors, pending sectors, or CRC errors can indicate an unreliable drive. Unusual noises like clicking or grinding are also serious warning signs of an impending hard drive failure.
- One or More Drives Aren’t Detected: If the drive is not detected by the NAS controller or if you’ve experienced multiple drive failures in a short period, it’s crucial to investigate the root cause before rebuilding. Attempting a rebuild with a failing drive could lead to corrupt data.
- Controller Concerns: A malfunctioning RAID controller can jeopardize the entire rebuild process. Symptoms of a failing controller include system instability, unexpected reboots, and error messages related to the RAID array. Verify controller health through diagnostic tools provided by the manufacturer.
- Power and Environment: Ensure your power supply has sufficient capacity to handle the increased load during a rebuild (this is most applicable to enterprise systems; home RAID arrays are unlikely to fail due to power issues, provided that the electrical supply is reliable). Overheating can also be a concern, so make sure your NAS has adequate cooling.
NAS Rebuild Software Issues
A compromised file system can lead to data corruption during a rebuild. Before starting the rebuild, you might consider running file system check using tools like fsck (Linux) or chkdsk (Windows).
However, proceed with caution! While these utilities can identify and sometimes repair file system errors, they can also put extra stress on a failing drive. If you suspect drive problems, back up your data first and check SMART data for critical errors. If you do run chkdsk, start with the /f parameter for basic error checking.
Learn more: Don’t Use CHKDSK On a Failing Hard Drive
NAS RAID Configuration and Firmware Issues
Verify that your RAID configuration is consistent across all drives in the array. Mismatched parameters or inconsistencies can lead to a failed rebuild or data loss. Consult your NAS documentation to confirm the correct RAID settings.
It’s also worth noting that outdated NAS firmware or operating system software can introduce compatibility issues and increase the risk of rebuild failures. Always update to the latest stable versions before attempting a rebuild.
For those managing more complex NAS setups, there are additional factors to consider:
- Bit Rot and Data Degradation: Over time, data stored on hard drives can experience “bit rot,” where bits flip or become corrupted. Data scrubbing, a process that scans and verifies data integrity, can help mitigate this risk before a rebuild.
- SSD and NVMe Drives: Rebuilding SSDs and NVMe drives can be more challenging due to wear leveling algorithms and potential lifespan impact. Consult your drive manufacturer’s recommendations regarding rebuilds.
- RAID Level Specifics: Different RAID levels have unique considerations. RAID 5, for example, is more vulnerable to data loss during a rebuild than RAID 6. Factor in rebuild time and performance implications for your specific RAID configuration.
Related: What Happens During a Failed NAS Rebuild?
Rebuilding Any RAID Carries a Risk
Never attempt a NAS rebuild without a complete and verified backup of your data. A rebuild is not a backup solution: if it fails, you risk losing all your data. Implement a robust backup strategy that includes full, incremental, or differential backups to ensure data recoverability.
By carefully assessing your hardware, software, and data integrity, you can make informed decisions about when to proceed with a rebuild and when to seek alternative solutions.
Datarecovery.com provides comprehensive services for all NAS devices. Learn more about our NAS data recovery services or call 1-800-237-4200 to speak with an expert.
