🚀 NAS – P9 Configure RAID 1 on Synology NAS

2-Disk Mirroring Step-by-Step Guide

Data protection is one of the most critical aspects of any NAS deployment. Whether you’re building a home lab, a backup server, or a small business storage solution, disk redundancy should never be optional.

In this guide, you will learn how to configure RAID 1 on Synology NAS (2-disk mirroring) properly using DSM (DiskStation Manager).

RAID 1 ensures that your data is written identically to two disks. If one disk fails, your system continues running without data loss.

This tutorial is ideal for:

• 🏠 Home NAS users

• 🏢 Small and medium businesses (SMB)

• 💾 Backup storage systems

• 🖥️ IT administrators deploying Synology

By the end of this guide, you will have a fully mirrored and fault-tolerant NAS storage pool.

📌 What is RAID 1?

RAID 1 is a mirroring technology that duplicates data across two drives.

When using RAID 1:

• Disk 1 contains your data

• Disk 2 contains an exact copy

If one disk fails:

✔ System remains operational
✔ No data loss
✔ Easy disk replacement
✔ Fast recovery

However, keep in mind:

• Usable capacity equals one disk only

• Example: 2 × 4TB drives = 4TB usable space

RAID 1 prioritizes data redundancy over capacity.

🖥️ Step 1 – Install the Physical Drives

Before configuration:

1️⃣ Power off the Synology NAS
2️⃣ Insert two identical or similar-capacity drives
3️⃣ Power on the system

💡 Best Practice:

• Use NAS-rated drives (e.g., Seagate IronWolf, WD Red)

• Prefer identical models for optimal performance

Once installed, login to DSM via web browser.

⚙️ Step 2 – Open Storage Manager

In DSM:

1️⃣ Go to Storage Manager
2️⃣ Select Storage Pool
3️⃣ Click Create

Choose:

• Custom (for manual control)

• RAID Type → Select RAID 1

DSM may recommend SHR (Synology Hybrid RAID), but for strict mirroring, select RAID 1.

💾 Step 3 – Select the Two Disks

Choose both installed drives.

Confirm that:

• Both disks are healthy

• No important data exists (they will be formatted)

Proceed with initialization.

DSM will begin:

• Creating storage pool

• Synchronizing mirror

• Performing background parity check

⚠️ Important:

Initial synchronization may take several hours depending on disk size.

The system remains usable during this process.

📂 Step 4 – Create a Volume

After the storage pool is created:

1️⃣ Go to Volume
2️⃣ Click Create
3️⃣ Choose the RAID 1 storage pool

Select:

• Btrfs (recommended)

• Or EXT4 (if compatibility required)

💡 Btrfs Benefits:

• Snapshot support

• Data integrity protection

• Advanced recovery features

Complete the volume creation process.

🔍 Step 5 – Verify RAID 1 Status

To confirm correct configuration:

1️⃣ Open Storage Manager → Storage Pool
2️⃣ Check RAID type
3️⃣ Confirm status is “Healthy”

You can also view:

• Disk health

• Synchronization progress

• SMART information

Once healthy, RAID 1 is fully operational.

🛡️ What Happens if a Disk Fails?

If one disk fails:

• DSM sends notification

• Storage pool becomes “Degraded”

• System remains accessible

To recover:

1️⃣ Replace the failed disk
2️⃣ Go to Storage Manager
3️⃣ Click Repair

DSM will rebuild the mirror automatically.

This ensures continuous data availability.

🏢 Real-World Deployment Example

Small business example:

• 2 × 8TB NAS drives

• RAID 1 configuration

• Btrfs file system

• Snapshot enabled daily

• Hyper Backup configured to external storage

Result:

✔ Local redundancy
✔ Snapshot rollback capability
✔ External backup protection
✔ Minimal downtime risk

RAID 1 is often the first layer of a 3-2-1 backup strategy.

📊 RAID 1 vs Other RAID Types

RAID 1 vs RAID 0:

• RAID 0 → Performance only, no protection

• RAID 1 → Redundancy and stability

RAID 1 vs RAID 5:

• RAID 5 requires minimum 3 disks

• RAID 1 simpler for 2-disk systems

For 2-bay Synology models, RAID 1 is the safest configuration.

⚠️ Important Reminder

RAID 1 is NOT a backup.

It protects against:

✔ Single disk failure

It does NOT protect against:

❌ Accidental deletion
❌ Ransomware
❌ File corruption
❌ Fire or theft

Always combine RAID with:

• Snapshot

• External backup

• Cloud replication

🎯 Final Thoughts

Configuring RAID 1 on Synology NAS is one of the most important steps in building a reliable storage system.

With 2-disk mirroring, you achieve:

• Data redundancy

• High availability

• Easy recovery

• Professional NAS deployment

Whether you’re setting up a home NAS or deploying storage for an SMB, RAID 1 remains one of the most stable and trusted configurations.

Mastering RAID fundamentals is essential for every IT infrastructure professional.