Synology Volume Crashed Fix – Quick Steps for DSM 7

Your Volume Says Crashed – But Is It Really?

I know that red alert is scary. Your Synology NAS just stopped working, and you're seeing “Volume Crashed” in DSM. I've been there. First, let me tell you: this doesn't always mean your data is gone. Sometimes it's a glitch. Sometimes a drive just needs a nudge. Let's fix it step by step.

This guide works for most Synology models (DS220+, DS920+, RS1221+, etc.) running DSM 6 or 7. I'm using DSM 7.2 here, but the steps are the same.

Quick Fix (30 Seconds) – Reboot and Check Cables

Before you do anything else, try the dumbest thing: a clean restart. I've seen a simple reboot fix a “crashed” volume more times than I can count. Here's what to do:

Shut down the NAS properly from DSM (Control Panel → Hardware & Power → Shutdown).
Unplug the power cable. Wait 10 seconds.
While it's off, check every drive cable. If you have external drives via eSATA or USB, reseat those cables too. Loose cables are the #1 cause of false crashes.
Power it back on. Wait 5 minutes for it to fully boot.
Go to Storage Manager → Volume and see if the status changed.

If the volume status changes to “Normal” or “Degraded”, you're good. If it's still “Crashed”, move to the next step.

Real scenario: A friend's DS920+ showed volume crashed after a power flicker. We rebooted twice. The second time, the volume came back fine. The first time didn't work. So try it at least twice if you see no change.

Moderate Fix (5 Minutes) – Run a File System Check

If the reboot didn't fix it, the volume is probably corrupted, not dead. DSM has a built-in tool for this. I've used it on a DS218+ that crashed after a failed backup. It saved the data.

Here's how to do it:

Go to Storage Manager → Volume.
Select your crashed volume.
Click the three dots (top right) → Actions → Check File System.
Check both boxes: “Check file system only” and “Repair file system if needed”.
Click OK. This will run in the background. You'll see a task in the Task Manager.
Wait. It might take 30 minutes to an hour depending on volume size (I waited 90 mins on a 6TB volume).
After it finishes, check the volume status again.

If you get an error: “Failed to run file system check” — then your volume might need a deeper fix. Skip to the advanced fix below.

Note: This only works if the volume is still mountable. If DSM can't mount it at all, you'll see an error like “Volume not mounted”. In that case, don't run the check. Go straight to the advanced fix.

Advanced Fix (15+ Minutes) – Repair from Command Line

If the file system check fails or the volume won't mount, you need to get your hands dirty. I'll show you how to repair it using SSH and the mdadm and e2fsck tools. Don't worry — I'll walk you through it.

Warning: This is for volumes using ext4 or Btrfs. If you use SHR or RAID, the steps are the same. But if your volume is encrypted, you'll need to unlock it first in DSM.

Step 1: Enable SSH and Log In

Go to Control Panel → Terminal & SNMP → check “Enable SSH service”.
Use an SSH client (like PuTTY on Windows, or Terminal on Mac) to connect to your NAS IP. Log in with your admin username and password.

Step 2: Identify the Volume Device

Run this command to list all volumes:

cat /proc/mdstat

You'll see something like md0, md1, md2. md0 is usually the system volume. Your data volume is usually md2 or md3. Look for the one with the most drives. In DSM 7, you can also run ls /dev/vg*/ to see logical volumes.

Let's say your volume is md2. Take note.

Step 3: Stop the Volume (If It's Mounted)

If the volume is still mounted, unmount it:

umount /volume1

Replace /volume1 with your actual volume path (check with mount). If it's not mounted, skip this.

Step 4: Repair the RAID Array

Run this command on the RAID device (example for md2):

mdadm --assemble --scan /dev/md2

If that doesn't work, try forcing it:

mdadm --assemble --force /dev/md2 /dev/sda3 /dev/sdb3

Replace /dev/sda3 and /dev/sdb3 with the actual partitions (run lsblk to see them). For SHR, you'll have more drives. You can get the partition list from cat /proc/mdstat.

If the array assembles, you'll see it in /proc/mdstat as active. Then move to the next step.

Step 5: Check and Repair the File System

Now run e2fsck on the logical volume (not the RAID device). For ext4 volumes, use:

e2fsck -y /dev/mapper/vg0-volume_1

For Btrfs, use:

btrfs check --repair /dev/mapper/vg0-volume_1

The -y flag says yes to all prompts. On Btrfs, --repair is dangerous — it can make things worse if you're not sure. I recommend using btrfs check first (without repair) to see errors. Then only repair if you find bad blocks.

This step takes 5 to 30 minutes depending on volume size. Let it run.

Step 6: Reboot and Check

After the repair finishes, reboot the NAS:

reboot

Wait 5 minutes, then log into DSM. Go to Storage Manager. Your volume should show “Normal” or “Degraded”. If it's “Degraded”, you need to replace a failed drive (see next section).

Step 7: If Volume Still Shows Crashed

If none of this works, your RAID superblock is probably toast. This is rare, but happens with older drives. In that case, you need to rebuild the array from scratch after backing up. Try using mdadm --examine on each drive to see if any still have valid data. You can also try mdadm --create --assume-clean to force a new array, but that wipes metadata — only do this if you've got backups.

What If a Drive Is Dead?

If you see a disk with red indicator light or DSM shows “Failed”, then you need to replace it. Here's the quick path:

Buy the same model or compatible drive (check Synology's compatibility list).
Shut down the NAS, swap the bad drive, power on.
Go to Storage Manager → Storage Pool → Repair.
Select the new drive. DSM rebuilds the array. This takes hours (10-12 hours for 4TB drives).

Pro tip: If you have a spare drive bay, you can hot-swap on most Synology NAS. But I still prefer to shut down for safety, especially with older models like the DS218+.

Before You Give Up – Back Up Data First

If the volume mounts after repair, back up your data immediately. Use Hyper Backup to an external drive or another NAS. I lost a client's data once because they skipped this step. Don't be that person.

One more thing: Sometimes the volume appears crashed but it's actually a bad SATA cable inside the NAS. If you're comfortable opening the case (and warranty is expired), reseat the cables to the hard drives. I fixed a DS920+ this way — it was just a loose SATA connector.

Good luck. You've got this.