Synology SHR Calculator
Optimize Your NAS Storage with Synology Hybrid RAID Capacity Planning
Choose between single or double disk redundancy.
Enter Drive Sizes (TB)
0 TB
Visual storage distribution: Blue (Available), Green (Protection), Gray (Unused)
Used for Protection
Unused Space
Total Raw Capacity
| Metric | Capacity (TB) | Percentage |
|---|---|---|
| Data Storage | 0 TB | 0% |
| Data Protection | 0 TB | 0% |
| Unused Space | 0 TB | 0% |
What is Synology SHR Calculator?
A Synology SHR Calculator is an essential tool for NAS (Network Attached Storage) enthusiasts and IT professionals. Synology Hybrid RAID (SHR) is a proprietary automated RAID management system designed to make storage deployment quick and easy. Unlike traditional RAID levels like RAID 5 or RAID 6, which require all drives to be the same size for maximum efficiency, the Synology SHR Calculator demonstrates how mixed drive sizes can be utilized effectively.
Using a Synology SHR Calculator helps users plan their future expansions. If you start with two 4TB drives and later add an 8TB drive, SHR allows you to access more storage than a standard RAID 5 setup would. This flexibility is the primary reason why Synology remains a leader in the consumer and small business NAS market.
Synology SHR Calculator Formula and Mathematical Explanation
The math behind a Synology SHR Calculator is more complex than standard RAID. While standard RAID 5 uses (N-1) * Smallest_Drive, SHR slices drives into smaller chunks and applies RAID 1 or RAID 5 to those specific slices.
The simplified logic for the Synology SHR Calculator is:
1. Sort all drives from largest to smallest.
2. SHR-1: Available Capacity = (Sum of all drives) – (Largest Drive Capacity).
3. SHR-2: Available Capacity = (Sum of all drives) – (Sum of the two Largest Drives).
4. Constraint: Any space on the largest drive that cannot be mirrored or paritied with at least one (for SHR-1) or two (for SHR-2) other drives of equal size remains “Unused Space”.
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Total Capacity | Sum of all physical drive sizes | Terabytes (TB) | 2TB – 200TB |
| Fault Tolerance | Number of drive failures allowed | Drives | 1 (SHR) or 2 (SHR-2) |
| Redundancy Space | Capacity reserved for parity | Terabytes (TB) | Variable |
| Unused Space | Wasted space due to size mismatch | Terabytes (TB) | 0 – 18TB |
Practical Examples (Real-World Use Cases)
Example 1: Mixed Home Setup
A user has four drives: 10TB, 10TB, 4TB, and 4TB.
Using the Synology SHR Calculator for SHR-1:
– Total Capacity: 28TB
– Protection (Largest Drive): 10TB
– Usable Space: 18TB
In a standard RAID 5, these would be treated as 4x4TB, giving only 12TB usable and leaving 12TB wasted. The SHR configuration gains 6TB of extra space.
Example 2: Enterprise Expansion
A business uses SHR-2 for 2-disk fault tolerance with drives: 18TB, 18TB, 18TB, 10TB, 10TB.
– Total Capacity: 74TB
– Protection (Two Largest Drives): 18TB + 18TB = 36TB
– Usable Space: 38TB
This ensures that even if two drives fail simultaneously, no data is lost.
How to Use This Synology SHR Calculator
- Select your redundancy level: SHR-1 (1 drive failure protection) or SHR-2 (2 drive failure protection).
- Enter the capacity of each hard drive in the input slots provided. Leave empty or set to 0 for empty bays.
- The Synology SHR Calculator will automatically compute the usable space, protection space, and unused space.
- View the dynamic bar chart to see a visual representation of your NAS storage distribution.
- Use the “Copy Results” button to save your configuration for future purchase planning.
Key Factors That Affect Synology SHR Calculator Results
- Drive Count: SHR requires at least 2 drives. SHR-2 requires at least 4 drives.
- Mixing Sizes: To add larger drives to an existing SHR array, you must add at least two drives of the new larger size to utilize the extra space.
- Btrfs vs EXT4: While the Synology SHR Calculator estimates raw capacity, the file system takes a small overhead (approx 4-5%).
- Decimal vs Binary: HDD manufacturers use decimal (1TB = 1000GB), but DSM uses binary (1TiB = 1024GiB). This calculator uses decimal TB for simplicity.
- Expansion Limits: Older Synology models may have a 16TB or 108TB single volume size limit, regardless of the Synology SHR Calculator result.
- Drive Health: Redundancy protects against failure, but not against multiple failures during the “rebuild” phase.
Frequently Asked Questions (FAQ)
Yes, but you must add additional drives. The Synology SHR Calculator shows that SHR-2 requires a minimum of 4 drives.
For mixed drive sizes, yes. SHR provides more usable space and easier expansion than RAID 5.
In SHR-1, you will have 12TB usable, 4TB protection, and 14TB unused. SHR needs at least two of the largest drives to use their full capacity.
The performance impact of SHR compared to traditional RAID is negligible for most home and SMB users.
Yes, as long as the capacities are compatible with the SHR expansion rules.
Synology currently supports drives up to 22TB+ depending on the model compatibility list.
No, Synology reserves a small portion of every drive for the DSM operating system, which is not reflected in raw storage math.
Yes, SHR is a Synology-specific technology based on Linux LVM and RAID.
Related Tools and Internal Resources
- Synology RAID Calculator – Compare standard RAID levels like RAID 0, 1, 5, 6, 10.
- NAS Storage Comparison – A guide to picking the right NAS hardware for your storage needs.
- HDD Reliability Guide – Which drives last the longest in a NAS environment?
- RAID 5 Calculator – Specific tool for calculating RAID 5 arrays with identical drives.
- RAID 10 Calculator – Calculate speed and redundancy for RAID 10 stripping and mirroring.
- Backup Strategy Guide – Why RAID is not a backup and how to implement 3-2-1.