Raid Shr Crash Recovery |verified| Jun 2026

Review: RAID SHR Crash Recovery 1. What is SHR? (Quick Context) 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. 2. Common “Crash” Scenarios | Crash Type | Example | Recoverable? | |------------|---------|---------------| | Single disk failure | One disk dies, others OK | ✅ Yes (if SHR1) | | Two disks fail simultaneously | Two disks crash at once | ❌ No (SHR1) / ✅ Yes (SHR2) | | File system corruption | Sudden power loss, improper shutdown | ✅ Often yes (via fsck ) | | DSM crash (OS partition failure) | System won’t boot, but data disks intact | ✅ Yes (reinstall DSM) | | Accidental deletion + overwrite | User error | ⚠️ Limited (undelete tools) | | Metadata corruption (LVM/RAID) | Crash during RAID resync | ⚠️ Complex recovery | 3. Recovery Principles

Do not immediately rebuild with a new disk if the array is degraded but accessible — first backup critical data. Do not initialize disks or reset the NAS without understanding the failure. SHR recovery relies on:

/etc/mdadm.conf – RAID config LVM metadata – volume grouping Partition table on each disk (usually partition 3 = data)

4. Step-by-Step Recovery Workflow Phase 1 – Assessment raid shr crash recovery

Check Storage Manager → HDD/SSD status. Note which disk(s) are Failed , Initialized , or Missing . Run via SSH (if possible): cat /proc/mdstat mdadm --detail /dev/mdX lvm pvs vgdisplay

Phase 2 – Degraded but Bootable

Replace failed disk with same or larger size. In Storage Manager → Repair → Select new disk. Wait for resync (can take hours). Do not shut down. Review: RAID SHR Crash Recovery 1

Phase 3 – System Won’t Boot (DSM crash, disks OK)

Use Synology Assistant → Reinstall DSM. Choose “Keep my data” mode. After reinstall, Storage Manager will usually auto-mount the volume.

Phase 4 – Manual Recovery (Advanced, via Linux PC) If DSM fails to assemble the array: Unlike traditional RAID 5 or RAID 1, SHR

Connect all SHR disks to a Linux PC. Install mdadm , lvm2 . Scan for RAID superblocks: mdadm --assemble --scan --verbose

Activate LVM: lvscan vgchange -ay