A read-write SSD cache can hold data that has not yet reached the main storage volume. Switching the NAS off does not make that cached data unnecessary. Synology warns that removing SSDs before removing the cache through Storage Manager can cause data loss, including when the system is powered off.

This is a preparation check for planned maintenance on a healthy system. If the volume or cache is already crashed, missing or otherwise unhealthy, preserve its status and obtain the recovery procedure for that condition. Do not turn a failure investigation into an experimental cache-removal attempt.

Identify the cache and its volume

Record the NAS model, DSM version, cache type, associated volume and SSD identities. Read the allocation information rather than identifying a drive only by its size or bay position. Keep the maintenance notes alongside the current backup and recovery details for the affected data.

Synology's cache-type change procedure says the volume should be Healthy before cache removal. For DSM 7, it directs the administrator to Storage Manager, Storage, then the selected SSD cache's menu and Remove. DSM 6 uses a different SSD Cache page. Follow the installed version's instructions and read the displayed effect before confirming.

Wait for the software operation to finish

Schedule the work with people using the volume and allow the documented removal process to complete. A clicked confirmation is not the same as completed cache removal. Verify the resulting Storage Manager state and investigate any error before touching the hardware.

Only after logical removal has completed should the technician follow the model's hardware procedure for the intended SSDs. Some models and slots require different handling, so a generic instruction to pull a drive is insufficient. Match the serial numbers to the maintenance record at that stage.

After the planned hardware work, inspect the volume and share access and open a known non-sensitive document. Record whether a replacement cache was created or the volume now operates without one. Performance expectations may change, but preserving a working volume and verified data takes priority over immediately recreating the previous cache layout.

Sources: Synology documentation 1, Synology documentation 2.