Synology NAS Error Code 19: How to Fix It

Q: Will I lose my data when Synology shows Error Code 19?

Not necessarily. Error Code 19 means the RAID array is degraded, which is a warning state, not always a full data loss event. If only one drive has failed in a RAID 1, RAID 5, SHR, or similar redundant array, all your data is still intact on the remaining drives. You need to replace the failed drive and let DSM rebuild the array. Data loss only occurs if you have more drive failures than your RAID level can tolerate, or if you accidentally format the volume.

Q: How long does a Synology RAID rebuild take after replacing a drive?

RAID rebuild time depends heavily on the total drive capacity and the number of drives in the array. For a 4TB drive in a two-drive RAID 1, expect roughly 8 to 16 hours. For larger arrays like a 4-drive RAID 5 with 8TB drives, rebuilds can take 24 to 48 hours or longer. During this time the NAS remains usable but performance will be reduced. You can monitor exact progress in Storage Manager > Storage Pool.

Q: Can I use any hard drive to replace a failed Synology drive?

Technically yes, but Synology strongly recommends using NAS-rated hard drives — such as Seagate IronWolf, Western Digital Red, or Toshiba N300 — rather than desktop drives. NAS drives are engineered for 24/7 operation, vibration resistance in multi-drive enclosures, and longer mean time between failures. The replacement drive must be at least the same capacity as the failed drive; a larger drive is fine. Check Synology's compatibility list at synology.com/compatibility for your specific NAS model.

Q: What is the difference between a degraded RAID and a crashed volume on Synology?

A degraded RAID means one or more drives have failed but the array still has enough drives to maintain data integrity based on your RAID level — your data is still accessible and the array is still running. A crashed volume means the array has lost too many drives to maintain redundancy, or a critical error has occurred, and DSM can no longer mount the volume. A degraded state is recoverable by replacing the failed drive; a crashed volume may require professional recovery if no backup exists.

Q: Should I set up notifications so this never surprises me again?

Absolutely. Go to DSM > Control Panel > Notification and enable both email and push notifications (via the DS Finder app on your phone). Enable alerts for drive failures, volume status changes, and S.M.A.R.T. warnings. You should also schedule regular Data Scrubbing (Storage Manager > Storage Pool > Schedule Data Scrubbing) at least once a month, and run S.M.A.R.T. extended tests quarterly. Most importantly, follow the 3-2-1 backup rule: keep 3 copies of your data, on 2 different media types, with 1 copy offsite or in the cloud using Synology's C2 Backup service.

Abstract

Synology Error Code 19 appears when your DSM storage volume has crashed or your RAID array has entered a degraded state, usually because one or more hard drives have failed or been disconnected. This is a serious warning that your data is at risk, but in many cases the array can be repaired or rebuilt without data loss if you act quickly. Do not power off your NAS or remove any drives until you have assessed the situation carefully.