Synology RAID Calculator
A powerful tool to help you understand storage options for your Synology NAS. Calculate usable space and data redundancy for various RAID levels, including Synology Hybrid RAID (SHR).
Calculation Results
Protection
Calculations are based on the standard where 1 TB = 1000 GB. Actual formatted capacity may vary slightly.
What is a Synology RAID Calculator?
A Synology RAID calculator is a specialized tool designed to help users determine the usable storage capacity and data redundancy of a disk array in a Synology Network Attached Storage (NAS) device. Before committing to a specific configuration, you can simulate how different RAID types (Redundant Array of Independent Disks) will affect your total available space and data protection level. This is crucial for planning and budgeting your storage needs, whether for a home media server or a business-critical data repository.
Unlike a generic NAS storage calculator, a Synology-specific calculator accounts for Synology Hybrid RAID (SHR and SHR-2), proprietary RAID implementations that offer more flexibility and optimized storage when using disks of varying sizes.
Synology RAID Formula and Explanation
The calculation for usable space depends entirely on the chosen RAID level. Each level has a different formula that balances performance, storage capacity, and fault tolerance. Let’s denote the variables first.
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| N | Number of Disks | Unitless (Count) | 2 – 24+ |
| S | Size of Smallest Disk | TB or GB | 1 – 22+ |
Formulas by RAID Type:
- SHR: Usable Space ≈ (Sum of all disk sizes) – (Size of one largest disk). This is an approximation; SHR is more complex as it creates optimal RAID-5-like arrays from disks. With same-sized disks, it’s identical to RAID 5.
- SHR-2: Usable Space ≈ (Sum of all disk sizes) – (Size of two largest disks). Offers 2-disk fault tolerance, similar to RAID 6.
- RAID 0: Usable Space = N * S. Offers no data protection.
- RAID 1: Usable Space = S. Requires at least 2 disks. All data is mirrored.
- RAID 5: Usable Space = (N – 1) * S. Requires at least 3 disks.
- RAID 6: Usable Space = (N – 2) * S. Requires at least 4 disks.
- RAID 10: Usable Space = (N / 2) * S. Requires an even number of disks, minimum 4.
Understanding the difference between RAID 5 vs RAID 6 is a critical step in deciding your storage strategy, balancing capacity against an extra layer of protection.
Practical Examples
Example 1: Home Media Server (SHR)
A user wants to set up a Synology DS423+ for a Plex media server and personal backups. They have purchased 4 disks of 8 TB each.
- Inputs: Number of Disks = 4, Disk Size = 8 TB, RAID Type = SHR
- Calculation: Since all disks are the same size, SHR behaves like RAID 5. Usable Space = (4 – 1) * 8 TB.
- Results:
- Usable Space: 24 TB
- Protection: 8 TB
- Fault Tolerance: 1 disk
Example 2: Small Business File Server (RAID 6)
A small business needs reliable storage for critical documents on a Synology DS923+. They prioritize data safety and opt for 6 disks of 4 TB each in a RAID 6 configuration.
- Inputs: Number of Disks = 6, Disk Size = 4 TB, RAID Type = RAID 6
- Calculation: RAID 6 uses two disks for parity. Usable Space = (6 – 2) * 4 TB.
- Results:
- Usable Space: 16 TB
- Protection: 8 TB
- Fault Tolerance: 2 disks
How to Use This Synology RAID Calculator
Using this calculator is a straightforward process to help you plan your storage array effectively.
- Enter the Number of Disks: Input the total quantity of physical hard drives you plan to install in your NAS.
- Set the Disk Size: Enter the capacity of a single drive and select the correct unit (TB or GB). This Synology RAID calculator assumes all drives are of identical size for simplicity in standard RAID levels. For SHR, the true benefit comes from mixing sizes, which is explained in our guide to Synology SHR.
- Select the RAID Level: Choose your desired RAID configuration from the dropdown menu. The calculator will automatically show an error if you don’t meet the minimum disk requirement for a selection.
- Review the Results: The calculator instantly provides the total usable space, the amount of space dedicated to data protection, and the number of disks that can fail without data loss. The visual bar chart helps you quickly grasp the ratio of usable to protected capacity.
Key Factors That Affect Synology RAID Performance
While this Synology RAID calculator focuses on capacity, several other factors influence the real-world performance of your NAS.
- Disk Speed (RPM): Drives at 7200 RPM generally offer faster read/write speeds than 5400 RPM drives, which is noticeable when accessing many small files.
- Disk Type (HDD vs. SSD): SSDs provide dramatically faster access times and throughput than traditional HDDs, making them ideal for running virtual machines or hosting databases, but at a higher cost per gigabyte.
- Cache: Using M.2 NVMe SSDs as a read/write cache in a Synology NAS can significantly boost performance for frequently accessed data without requiring a full SSD array.
- Network Connection: A 1GbE network connection can be a bottleneck. Using a 2.5GbE, 10GbE, or bonded connection is crucial for achieving the maximum speed your RAID array can deliver. A network bandwidth calculator can help you understand your limits.
- CPU of the NAS: The processing power of the Synology unit itself can limit performance, especially with software-intensive tasks like RAID 5/6 parity calculations or file encryption.
- Workload Type: Performance varies based on the workload. Sequential reads/writes (like video streaming) are typically faster than random reads/writes (like running a database).
Frequently Asked Questions (FAQ)
1. Can I mix disk sizes in a Synology NAS?
Yes, especially with SHR (Synology Hybrid RAID). SHR is designed to optimize storage capacity when using disks of different sizes. Standard RAID levels (like RAID 5) will treat all disks as if they were the size of the smallest disk in the array, wasting capacity.
2. What’s the difference between RAID 5 and SHR?
With disks of the same size, they are functionally identical (1-disk protection). The key difference appears with mixed-size disks, where SHR can create multiple underlying RAID volumes to utilize the full capacity of the larger disks. For a deeper dive, see our article on the best RAID for Plex.
3. What does “disk fault tolerance” mean?
It’s the number of hard drives that can fail in your RAID array simultaneously without you losing any data. RAID 5 and SHR have a 1-disk fault tolerance, while RAID 6 and SHR-2 have a 2-disk fault tolerance.
4. Should I use RAID 0?
Generally, no. RAID 0 offers the best performance and 100% capacity utilization but has zero fault tolerance. If any single drive fails, all data on all drives is lost. It’s only suitable for temporary or scratch data where speed is the only priority.
5. Why is the usable capacity less than the total size of my disks?
This is due to data redundancy. In all RAID levels except RAID 0, a portion of the disk space is used to store parity information or a direct mirror of the data. This “protection space” is what allows the array to be rebuilt if a drive fails.
6. Is RAID a backup?
No, RAID is not a backup. RAID provides redundancy against hardware failure (a disk failing). It does not protect against file deletion, corruption, viruses, or catastrophic events like fire or theft. You must always maintain a separate backup strategy (e.g., to an external drive or cloud service).
7. What is RAID 10?
RAID 10 (or RAID 1+0) combines mirroring and striping. It requires an even number of disks (min 4). It stripes data across mirrored pairs. This offers excellent read/write performance and 1-disk fault tolerance within each mirrored pair, making it a popular choice for business applications.
8. Why does the formatted capacity in DSM differ from this calculator?
This Synology RAID calculator uses the marketing standard (1 TB = 1000 GB). Operating systems, including Synology’s DSM, often use the binary standard (1 TiB = 1024 GiB). Additionally, the file system itself consumes a small amount of space for metadata. This leads to a small discrepancy.