Raid Synology Calculator

Estimate storage capacity for DiskStation and RackStation NAS devices.

What is a RAID Synology Calculator?

A raid synology calculator is a specialized utility designed to help NAS (Network Attached Storage) owners estimate the actual usable storage space they will have after accounting for redundancy and file system overhead. Unlike basic RAID arrays, Synology offers unique configurations like SHR (Synology Hybrid RAID), which allows for mixing drive sizes—a feature that standard raid synology calculator logic must specifically account for.

Who should use this? Anyone planning a new NAS purchase or upgrading existing drives. A common misconception is that if you buy four 10TB drives, you get 40TB of space. In reality, depending on your RAID choice, you might only see 20TB or 30TB of usable capacity. This raid synology calculator bridges the gap between hardware specs and real-world availability.

RAID Synology Calculator Formula and Mathematical Explanation

The mathematical approach changes based on the redundancy level. Traditional RAID (0, 5, 6, 10) uses fixed formulas based on the smallest drive in the set, while SHR uses a more flexible algorithm.

Core Formulas Used:

• RAID 0: Sum of all drive capacities.
• RAID 1: Capacity of the smallest drive (data mirrored).
• RAID 5: (Total Drives – 1) × Smallest Drive Capacity.
• RAID 6: (Total Drives – 2) × Smallest Drive Capacity.
• SHR: Total capacity minus the capacity of the largest drive.
• SHR-2: Total capacity minus the capacity of the two largest drives.

Variable	Meaning	Unit	Typical Range
N	Number of Drives	Count	2 – 24
C_min	Smallest Drive Capacity	TB	1 – 22
C_max	Largest Drive Capacity	TB	1 – 22
S_total	Sum of all Capacities	TB	2 – 500+

Practical Examples (Real-World Use Cases)

Example 1: The Home User (SHR)

A user has a 4-bay Synology NAS with two 4TB drives and two 8TB drives. Using the raid synology calculator with SHR logic:

• Inputs: 4TB, 4TB, 8TB, 8TB.
• Calculation: SHR mirrors the 4TB blocks across all drives and stripes the remaining 4TB on the larger drives. Mathematically for SHR, it’s (4+4+8+8) – 8 = 16TB.
• Output: 16TB Usable, 8TB Protection, 0TB Unused.

Example 2: The Enterprise Archive (RAID 6)

A business uses six 12TB drives in a RackStation. Because they prioritize data safety, they choose RAID 6.

• Inputs: 6 x 12TB.
• Calculation: (6 – 2) × 12 = 48TB.
• Output: 48TB Usable, 24TB Protection.

How to Use This RAID Synology Calculator

1. Select RAID Level: Choose your desired redundancy level (e.g., RAID 5 for 1-drive failure protection).
2. Input Drive Sizes: Enter the capacity of each drive currently in or planned for your NAS.
3. Review Results: The raid synology calculator will instantly update the “Available Storage” and “Protection Space.”
4. Check the Chart: View the visual breakdown to ensure you aren’t leaving “Unused Space” due to incompatible drive sizes in traditional RAID modes.

Key Factors That Affect RAID Synology Calculator Results

• Drive Failure Tolerance: RAID 1, 5, and SHR allow 1 drive to fail. RAID 6 and SHR-2 allow 2 drives to fail. Higher protection reduces usable space.
• Binary vs. Decimal (TB vs TiB): Drive manufacturers use decimal (1000^4), but Synology DSM uses binary (1024^4). Your actual capacity in DSM will be roughly 9% lower than the physical label.
• Btrfs/EXT4 Overhead: The file system itself consumes about 4-5% of the usable space for metadata and indexing.
• Unused Space: In traditional RAID 5, if you mix a 10TB drive with 4TB drives, the extra 6TB on the large drive is wasted. Our raid synology calculator identifies this.
• Hot Spares: If you designate a drive as a hot spare, it provides 0TB of storage and is not counted in the raid synology calculator primary total.
• Expansion Limits: Some older Synology models have a 16TB or 108TB single volume size limit, regardless of the RAID calculation.

Frequently Asked Questions (FAQ)

Does SHR provide better storage than RAID 5?

Yes, specifically when using mixed drive sizes. SHR optimizes the layout to use “leftover” space that RAID 5 would ignore. Use our raid synology calculator to compare the two.

What is “Unused Space” in the calculator?

Unused space occurs in traditional RAID levels when drives have different capacities. The array is limited by the smallest drive, leaving the extra capacity on larger drives inaccessible.

How many drives do I need for RAID 10?

RAID 10 requires a minimum of 4 drives and must always be an even number. It offers excellent performance by combining mirroring and striping.

Can I change my RAID type later?

Synology allows upgrading from RAID 1 to RAID 5, or SHR-1 to SHR-2, but you usually cannot “downgrade” without formatting. Always check the raid synology calculator before initial setup.

What happens if two drives fail in RAID 5?

In RAID 5 (or SHR-1), your data is lost if two drives fail simultaneously. Use RAID 6 or SHR-2 if you need 2-drive failure protection.

Is the 16TB volume limit still a thing?

Only on older 32-bit CPU models. Most modern Plus series units support at least 108TB per volume.

Does drive speed (7200 vs 5400 RPM) affect capacity?

No, speed affects performance (IOPS), but the raid synology calculator results remain the same regardless of RPM or cache size.

Should I use Btrfs or EXT4?

Btrfs is recommended for Synology as it supports snapshots and data self-healing, though it has a tiny bit more overhead than EXT4.

Related Tools and Internal Resources

• NAS Storage Capacity Planner – Plan your future storage growth and hardware costs.
• HDD vs SSD NAS Comparison – Decide which drive technology is right for your raid synology calculator results.
• Synology Model Finder – Match your storage needs with the right NAS hardware.
• UPS Backup Calculator – Ensure your RAID array stays safe during power outages.
• Network Speed Calculator – See how long it takes to fill your calculated RAID storage.
• Data Scrubbing Scheduler – Keep your RAID healthy and prevent silent data corruption.