Can I replace a failed HDD with an SSD in a RAID 1 QNAP NAS?

Last modified date: 2026-03-12

Applicable Products

QNAP NAS models that support RAID 1 (for example, 2-bay models such as TS-251)

Scenario

The NAS currently uses two 3.5-inch HDDs configured as a RAID 1 array.
One HDD has failed. The user wants to know whether the failed HDD can be replaced with an SSD.

Explanation

RAID 1 mirrors data between two drives. The usable capacity of the RAID 1 group is determined by the smallest member drive. To successfully rebuild the RAID 1 array, the replacement drive must provide at least the same usable capacity as the existing member.

In many QNAP NAS models, it is technically possible to mix an HDD and an SSD in the same RAID 1 group, as long as the drive is supported and meets capacity requirements. However, overall performance and behavior are still constrained by the RAID configuration and system design, and the array will not perform like an all-SSD RAID.

Solution

You can usually replace a failed HDD with an SSD in a RAID 1 QNAP NAS if the SSD is supported for your NAS model and has equal or larger usable capacity than the original drive. A smaller-capacity drive is not recommended because the RAID 1 array may not be able to rebuild.

Step-by-step procedure

Confirm your current RAID type, original drive capacity, and NAS model in QTS (for example, in Storage > Storage/Snapshots).
Select a replacement SSD that:
- is listed as compatible with your NAS model on the QNAP Compatibility List, and
- has equal or larger capacity than the failed HDD.
Follow the QTS instructions to replace the failed disk and start the RAID 1 rebuild.
Monitor the RAID rebuild status until it completes and the RAID group status changes to Healthy.
After the rebuild finishes, run a disk and volume health check and confirm that read/write operations complete normally.

Validation

RAID 1 status is Healthy in QTS.
No critical disk, storage pool, or volume warnings are displayed.
File read/write operations complete without errors.

Risk reminder

RAID rebuild operations always carry some risk, especially if the remaining drive is old or has marginal health. Disk model, firmware, and age can affect rebuild reliability. Before replacing drives or rebuilding RAID, ensure that you have a verified backup of critical data.