If SHR-1 has one failed drive, the pool is "Degraded" but still functional. Replace the faulty drive with a healthy one of equal or greater size. In Storage Manager , select the pool and choose Action > Repair . Advanced Recovery via PC (Ubuntu)
Synology Hybrid RAID (SHR) is a proprietary system that combines multiple disk sizes into one volume, using Linux MD RAID (for redundancy) and LVM (for flexible space allocation). Unlike traditional RAID 5 or RAID 1, SHR can use mismatched drives. raid shr crash recovery