How to Replace a Failing NAS Drive (Updated January 2026)
A failed NAS drive isn’t a rare exception — When a drive starts throwing warnings or goes offline, it’s not just a convenience issue anymore; it’s about keeping your data available and your RAID/storage pool stable. With the right preparation, you can replace a bad NAS drive cleanly in most setups.
In this guide, you’ll learn how to spot common warning signs early, choose a suitable replacement drive, and prepare the swap so the rebuild runs smoothly and under control.
What You Learned
- How to recognize a failing NAS drive using real-world symptoms (noises, slow performance, crashes) and S.M.A.R.T. health checks in your NAS interface.
- How to choose the right replacement drive by focusing on NAS-rated models, matching or increasing capacity, and balancing performance and reliability.
- How to safely prepare for a drive swap by verifying backups, identifying the correct bay, checking compatibility, and documenting your current drive layout.
- When to use hot swap vs. cold swap and the limitations of hot-swapping, especially for HDDs vs. SSDs and M.2 slots.
- How to replace a failed drive and rebuild RAID step by step, plus what to do in worst-case scenarios—like having no recent backup or facing serious drive damage—without making data loss more likely.
Identifying a Failing NAS Drive
Before you replace a NAS drive, you should first make sure there’s actually a drive problem—and not an issue with a cable, slot, or configuration. In this section, you’ll learn the typical warning signs and how to check them directly in your NAS interface using simple status and S.M.A.R.T. tests.
Common Signs of a Failing NAS Drive
Here are the red flags to watch for:
- Unusual Noises: If your NAS drive starts making clicking, grinding, or whining sounds, it could be a sign of mechanical failure.
- Slow Performance: If your NAS is taking longer than usual to load files or transfer data, it might be struggling to read from a failing drive.
- Error Messages: Keep an eye out for error messages in your NAS software or system logs. These can be early warnings of drive issues.
- Frequent Crashes or Freezes: If your NAS system starts crashing or freezing more often, it could be due to a failing drive.
Not all signs are obvious, and sometimes drives fail without warning. That’s why regular monitoring is crucial.
Using Diagnostic Tools
Most NAS drives come with a built-in diagnostic tool called SMART (Self-Monitoring, Analysis, and Reporting Technology). It’s like a health check for your drive, monitoring things like temperature, error rates, and more. You can access SMART data through your NAS software or using third-party tools like CrystalDiskInfo.
Here’s how to check SMART data on our UGREEN NAS devices:
- Open your NAS software and navigate to the drive management section (Storage).
- Look for a SMART or health status option for each drive (Hard Drive then select the Hard Drive you want to check, click on the 3 little dots and select Status Test).
- Check the Test result, ideally, it should say “Normal”.
- For more detailed data, you can also click on the 3 dots and select Detail, then S.M.A.R.T. Information.
If you’re not sure what the numbers mean, don’t worry. Most NAS software will flag any issues in plain language, like “Drive health is critical.”
Choosing the Right Replacement Hard Drive
Choosing the right drive isn’t just about plugging in any old hard drive; it’s about finding one that matches your NAS’s needs and maybe even gives it a boost. Break it down into the essentials: compatibility, capacity, performance, and reliability.
- Compatibility: Drives designed for NAS use, like Western Digital Red or Seagate IronWolf, are built to handle the constant workload of a storage system, unlike standard desktop drives.
- Capacity: Your new drive needs to match the capacity of the one it’s replacing to keep your RAID array happy. But this is also your chance to upgrade if you’re running low on space.
- Performance: How fast your NAS feels depends partly on the drive. You’ve got options, HDDs for bulk storage or SSDs for speed, and each has its perks.
- Reliability: NAS drives don’t get downtime, WD Red and IronWolf come with features like vibration protection and error correction, tailored for NAS life.
Click to read more: Top 6 Quietest NAS Drives for Home Use.
Preparing for the Drive Replacement
Good preparation reduces the risk of data loss and helps prevent you from accidentally pulling the wrong drive. The goal is simple: verify your backup, clearly identify the affected bay, and have a compatible replacement drive ready. If you’re unsure about your backup, a short overview of NAS backup methods can help you quickly choose and test the right option (USB drive, cloud backup, or a second copy on another device).
1) Create and briefly test a backup
Back up your most important data to an external drive or to the cloud. Then check: Restore at least one test file to make sure the backup is actually usable.
2) Clearly identify the affected drive
Open the storage manager and note the slot/bay number, the type of error (SMART, bad sectors, etc.), and your RAID configuration (for example RAID 1 or RAID 5). Then verify: Confirm that the bay number shown in the dashboard matches the physical drive position on the NAS.
3) Check the replacement drive
Make sure the new drive is compatible and, in most RAID setups, is the same size or larger than the old one. Then verify: Compare the model/series against the vendor’s compatibility list and confirm the capacity in the technical specs.
4) Do a quick documentation pass
Take a photo of the current drive layout (which drive is in which bay), and label the trays if needed. Then verify: You can clearly tell later which drive was replaced and where it was originally installed.
Next, you’ll confirm whether your model supports hot swap or if it’s safer to replace the drive with the NAS powered off. After that comes the physical swap and starting the RAID rebuild.
Hot Swap vs. Cold Swap: Do You Need to Power Off the NAS?
One of the most common questions when replacing a drive is: “Do I have to shut down my NAS?” The answer depends on your model and your risk tolerance. In practice, there are two approaches:
- Hot swap (replace while powered on): UGREEN NASync series devices support hot swapping for hard drives. That means you can pull the failed drive and insert the new one without shutting the system down.
- Cold swap (replace while powered off): If you’re unsure or using an older NAS model, powering the device down first is the safest option.
UGREEN NAS Important Notice: Hot-Swapping Support Limitations
Hot-swapping functionality is exclusively supported for HDDs installed in standard drive bays.
⚠️ Important restrictions:
Hot swapping is not supported in the following cases:
- SSDs installed in standard drive bays
- SSDs installed in M.2 expansion slots
How to Replace a Failed Drive in a UGREEN NAS
- Shut down the NAS from the web interface, wait until it is completely powered off, then disconnect the power cable before removing the drive.
- Unlock the drive tray with the key, press the latch so the handle pops out, and gently pull the tray out of the bay.
- Carefully label the failed drive (bay number, date, “failed”) and set it aside in case you later need professional data recovery.
- For 3.5" HDDs: Turn the tray over, press the Press latch to release the clamp arm, place the drive so the side holes line up with the tray pins, then push the clamp arm back to lock it in place.
- For 2.5" drives: Move the rear mounting pin into the fixed hole, align the bottom screw holes of the drive with the tray, secure it with screws, then reinsert the tray into the bay and lock it.
How to Restore or Rebuild Your Storage
If you’re using RAID (for example RAID 1, 5, or 6):
- Power the NAS back on (or, if you used hot swap, wait until the system detects the new drive) and open the UGREEN NAS OS interface.
- Go to the storage / RAID / pool status page, select the affected pool, choose the entry for the failed drive, and use the Replace or Repair/Rebuild option to add the new drive as a member.
- Wait for the RAID to fully rebuild / resilver. On large arrays this can take many hours or longer, and performance may be reduced while the rebuild is running.
⚠️ Never replace more than one drive at the same time while a rebuild is in progress. If you pull two drives at once in a RAID 1 or RAID 5 array, your data will be permanently lost.
No Backup? What to Do in a Critical Data Loss Situation
This is the scenario every user dreads: a drive has failed and your last backup is months old—or doesn’t exist. Before you panic or spend money on expensive tools, follow these steps to limit the damage.
1. Check if the volume is just “Degraded”
If you’re using RAID 1 (mirroring) or RAID 5 and “only” one drive has failed, your data is still there. Your NAS switches into what’s called degraded mode.
- The most important step: Do not try to repair the RAID immediately. As long as the NAS is still running, copy your most important files to an external USB drive or your computer right away.
- Only after your critical data is backed up should you replace the failed drive and start the rebuild. The rebuild process is heavy work for the remaining drives—if another one fails during this time, your data will be lost.
2. The trap: Connecting a NAS drive directly to a PC
Many users pull the old drive, connect it to a Windows PC with a USB adapter, and get a nasty surprise: Windows asks, “You need to format the disk in drive X: before you can use it. Do you want to format it?”
Why does this happen? NAS systems (including UGREEN) use Linux file systems such as EXT4 or Btrfs. Windows uses NTFS. It’s like trying to read a French book when you only speak English.
The DIY solution: To recover data on a PC, you need software that can read Linux partitions. Proven tools for home users include:
- Linux Reader (DiskInternals): A free Windows tool that lets you access EXT4/Btrfs drives without modifying them.
- Ubuntu Live USB: For advanced users—boot your PC from a Linux USB stick to get native access to the drive.
3. When you need a professional
Software can only help with logical issues (accidental deletion, file system errors). If your drive is making mechanical noises (clicking, scraping, beeping) or won’t spin up at all:
- Shut the power off immediately. Every additional attempt to spin up the drive can scratch the magnetic surface and make recovery impossible.
- At this point, software cannot fix it. You’ll need a professional data recovery service that can open the drive in a cleanroom. It’s expensive (often several hundred dollars), but often the only way to save irreplaceable data.
