Knowledge Base

Why can’t the Raid 1 volume be seen on the NAS540?


A user created RAID 1 with 2 HDDs (a 300GB HDD and a 2TB HDD) then later removed the 300GB HDD and replaced it with a 2TB HDD.

While Raid 1 is under repair, the user created a Basic with a 100G SSD.

The user powered off the NAS and plugged the 300G HDD back into the NAS slot. The user then rebooted the NAS causing all volumes to disappear. However when checking the SMART status, the HDDs still exist although everything under Storage is missing.


Since disk A has the same Array UUID as disk B and disk C, the NAS system considers A as a disk member of RAID 1 and causes the NAS540 to assemble the RAID when booting. RAID 1 acknowledges that there are only two disks and that the size of A is not consistent with the RAID. Due to this, the system fails to assemble the RAID and causes the aforementioned problem.

To resolve this issue, remove disk A from the NAS and reboot the device. The Raid 1 volume should appear and work.
If the user wants to keep using disk A, the disk must be formatted before plugging back into the NAS540.


Environment preparation:

HDDs: Disk A: 150G, Disk B: 2TB, Disk C: 2TB, Disk D: 4TB

Model: NAS540


1. Create Raid 1 with disk A and disk B.

2. Swap disk A to disk C (Slot 3), and repair the Raid 1 volume.

3. While the Raid 1 volume is resyncing, create a new Basic with disk D.

4. When the resyncing process is finished, shut down the NAS540.
5. Plug disk A back into slot 1, and power on the NAS540.
6. The storage status will show that it is in danger, and the Raid 1 volume disappears. Check the hard disk status, all disks show up as healthy but the HDD space has not been used except the space occupied by the Basic.


Please leave your comment:


Question Profile


Still have trouble with your device? Contact Zyxel technology support team directly!

Contact Zyxel Support