Synology RAID Calculator
Estimate usable storage, redundancy, and drive requirements for your Synology NAS.
Synology RAID Configuration Summary
RAID Capacity Comparison
RAID Type Details
| RAID Type | Minimum Drives | Fault Tolerance | Usable Capacity Formula | Typical Use Case |
|---|---|---|---|---|
| SHR | 2 | 1 drive failure (or 2 if using 2+ drives of same size) | (N – 1) * Drive Size (for 2 drives) or (N – F) * Drive Size where F is min drives for redundancy, optimized | Flexibility and ease of expansion, especially with mixed drive sizes. |
| RAID 1 | 2 | 1 drive failure | (N – 1) * Drive Size | Simple redundancy, mirrored data. |
| RAID 5 | 3 | 1 drive failure | (N – 1) * Drive Size | Balance of capacity and redundancy, good for general use. |
| RAID 6 | 4 | 2 drive failures | (N – 2) * Drive Size | Higher redundancy, suitable for large arrays or critical data. |
| RAID 10 | 4 (even number) | 1 drive failure per mirrored pair | (N / 2) * Drive Size | Performance and redundancy, requires more drives. |
What is a Synology RAID Calculator?
A Synology RAID calculator is a specialized tool designed to help users determine the potential storage capacity and data redundancy of a Synology Network Attached Storage (NAS) device based on various RAID (Redundant Array of Independent Disks) configurations. Synology offers its own flexible solution called Synology Hybrid RAID (SHR), alongside standard RAID levels like RAID 1, RAID 5, RAID 6, and RAID 10. This calculator simplifies the complex calculations involved in understanding how many drives you need, the size of each drive, and the resulting usable storage space after accounting for parity or mirroring.
Who Should Use It: Anyone planning to set up a Synology NAS for the first time, expanding an existing NAS, or evaluating different RAID options for data protection and storage efficiency. This includes home users, small businesses, and IT professionals.
Common Misunderstandings: A frequent point of confusion is that the 'usable' capacity is always the sum of all drive sizes. In reality, RAID configurations use a portion of the total raw capacity for redundancy (parity data or mirroring), reducing the final usable space. Another is the assumption that all RAID types offer the same level of fault tolerance; this varies significantly, with RAID 6 and SHR (with multiple drives) offering the highest protection against drive failures.
Synology RAID Calculator Formula and Explanation
The core of any RAID calculator involves understanding how drive count, individual drive size, and the chosen RAID level impact usable capacity and fault tolerance. The formulas differ significantly between RAID types.
Key Formulas:
- Raw Capacity: Number of Drives × Drive Size
- RAID 1 (Mirroring): Usable Capacity = (Number of Drives – 1) × Drive Size. One drive's capacity is used for mirroring.
- RAID 5 (Parity): Usable Capacity = (Number of Drives – 1) × Drive Size. One drive's capacity is used for parity information.
- RAID 6 (Dual Parity): Usable Capacity = (Number of Drives – 2) × Drive Size. Two drives' capacities are used for parity.
- RAID 10 (Stripe of Mirrors): Usable Capacity = (Number of Drives / 2) × Drive Size. Half the drives are used for mirroring.
- SHR (Synology Hybrid RAID): This is more complex. For two drives, it functions like RAID 1. With more drives, it optimizes storage by creating multiple RAID arrays. The general idea is (Total Drives – Minimum Drives for Redundancy) × Drive Size, but it intelligently utilizes space from larger drives. For this calculator, we simplify SHR to function similarly to RAID 5 for capacity estimation when redundancy is single-drive failure, and RAID 6 when double-drive failure is selected, assuming drives are of equal size.
Variables Table:
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| N (Number of Drives) | Total physical drives in the storage pool. | Unitless | 2+ |
| S (Drive Size) | Capacity of a single physical drive. | TB, GB, PB | 1 TB – 20 TB+ |
| F (Fault Tolerance) | Number of drives that can fail without data loss. | Unitless | 0, 1, or 2 |
| U (Usable Capacity) | Total storage space available for data after accounting for RAID overhead. | TB, GB, PB | Varies greatly based on N, S, and RAID type. |
| O (Overhead/Parity) | Capacity used for redundancy (parity or mirroring). | TB, GB, PB | Typically equivalent to 1 or 2 drive sizes, or N/2 for RAID 10. |
Practical Examples
Let's illustrate with realistic scenarios:
Example 1: Home Media Server Setup
- Goal: Store large media files with protection against a single drive failure.
- Inputs:
- RAID Type: Synology Hybrid RAID (SHR)
- Number of Drives: 4
- Drive Size: 8 TB
- Desired Redundancy: Single Drive Fault Tolerance
- Calculation: SHR with 4 drives and single fault tolerance behaves similarly to RAID 5 in terms of capacity calculation for equal drive sizes. Overhead is roughly 1 drive.
- Results:
- Raw Capacity: 4 drives * 8 TB/drive = 32 TB
- Overhead/Parity: ~1 drive * 8 TB = 8 TB
- Usable Capacity: ~24 TB
- Fault Tolerance: 1 drive failure
Example 2: Small Business Backup
- Goal: Maximize storage for backups while ensuring high data protection against two drive failures.
- Inputs:
- RAID Type: RAID 6
- Number of Drives: 6
- Drive Size: 16 TB
- Desired Redundancy: Double Drive Fault Tolerance
- Calculation: RAID 6 uses two drives' worth of capacity for dual parity.
- Results:
- Raw Capacity: 6 drives * 16 TB/drive = 96 TB
- Overhead/Parity: 2 drives * 16 TB/drive = 32 TB
- Usable Capacity: ~64 TB
- Fault Tolerance: 2 drive failures
Example 3: Comparing RAID 1 vs SHR for Redundancy
- Goal: Understand capacity differences for basic redundancy.
- Inputs:
- RAID Type: RAID 1
- Number of Drives: 2
- Drive Size: 10 TB
- Desired Redundancy: Single Drive Fault Tolerance
- Calculation: RAID 1 capacity is based on one drive size.
- Results:
- Raw Capacity: 2 drives * 10 TB/drive = 20 TB
- Overhead/Parity: 1 drive * 10 TB = 10 TB
- Usable Capacity: ~10 TB
- Fault Tolerance: 1 drive failure
- Inputs (SHR):
- RAID Type: Synology Hybrid RAID (SHR)
- Number of Drives: 2
- Drive Size: 10 TB
- Desired Redundancy: Single Drive Fault Tolerance
- Calculation: SHR with 2 drives is equivalent to RAID 1.
- Results:
- Raw Capacity: 2 drives * 10 TB/drive = 20 TB
- Overhead/Parity: ~1 drive * 10 TB = 10 TB
- Usable Capacity: ~10 TB
- Fault Tolerance: 1 drive failure
- Note: While capacity is similar for 2 drives, SHR offers more flexibility when adding drives of different sizes later.
How to Use This Synology RAID Calculator
- Select RAID Type: Choose the RAID configuration you intend to use. SHR is recommended for most Synology users due to its flexibility.
- Enter Number of Drives: Input the total number of physical hard drives you will install in your Synology NAS. Ensure this meets the minimum requirement for your chosen RAID type (e.g., RAID 5 requires at least 3 drives).
- Specify Drive Size: Enter the capacity of a single drive. Use the dropdown to select the unit (TB, GB, or PB). For mixed-size drives in SHR, use the size of your smallest drive for a conservative estimate, or calculate based on multiple pools if needed.
- Choose Redundancy Level: Select how many drive failures your setup should tolerate. 'Single Drive Fault Tolerance' is common for RAID 5, SHR, and RAID 1. 'Double Drive Fault Tolerance' is characteristic of RAID 6. Note that 'No Redundancy' maximizes capacity but offers zero data protection.
- Interpret Results: The calculator will immediately display the estimated usable capacity, raw capacity, and fault tolerance. Pay close attention to the 'Usable Capacity' as this is the actual space available for your data.
- Select Units: You can change the drive size unit (TB/GB/PB) and the calculator will adjust the output units accordingly.
- Reset: Click 'Reset' to clear all fields and return to the default settings.
- Copy: Click 'Copy Results' to copy the summary to your clipboard.
Key Factors That Affect Synology RAID Capacity
- RAID Level: This is the most significant factor. RAID 0 offers maximum capacity but no redundancy, while RAID 1, 5, 6, and 10 all use capacity for data protection, reducing usable space.
- Number of Drives: More drives generally mean more raw capacity, but the RAID level dictates how much of that is usable. For RAID 5/6, more drives spread the parity overhead across more disks.
- Individual Drive Size: Larger drives directly increase both raw and usable capacity, assuming the RAID configuration can utilize it.
- SHR vs. Standard RAID: SHR's advantage lies in its ability to efficiently handle mixed drive sizes, maximizing usable capacity compared to standard RAID levels when drive sizes vary. Standard RAID typically requires drives of the same size for optimal performance and capacity.
- Drive Formatting and OS Overhead: The Synology DSM operating system and file system (like Btrfs or ext4) consume a small amount of space. This calculator provides an estimate, and actual usable space might be slightly less.
- Multiple Storage Pools: Synology DSM allows for multiple storage pools. If you create separate pools (e.g., one SHR pool and one RAID 1 volume), the capacity calculation applies per pool. This calculator assumes a single storage pool configuration.
- Drive Failure Tolerance: Selecting double-drive fault tolerance (RAID 6 or SHR with 2+ drives configured for it) inherently reduces usable capacity compared to single-drive fault tolerance.
FAQ about Synology RAID
A: Yes, SHR is designed to handle mixed drive sizes efficiently. It will use the largest possible drives for storage while allocating space effectively. For optimal capacity, it's still best to use similar-sized drives, but SHR prevents wasting significant space.
A: If a drive fails and your RAID configuration has fault tolerance (e.g., RAID 1, 5, 6, SHR), your NAS will continue to operate in a degraded state. You'll receive a notification to replace the failed drive. Once replaced, the NAS will rebuild the data onto the new drive.
A: For most users, especially those who might upgrade or mix drive sizes later, SHR offers superior flexibility and ease of management. Standard RAID levels (like RAID 5 or 6) offer predictable capacity and performance characteristics but are less forgiving with mixed drive sizes.
A: With 4 drives of the same size, SHR provides the same usable capacity as RAID 5 (3 drives worth of space). SHR's advantage shines when you add a larger drive later; it can utilize the extra space, whereas standard RAID 5 would only use the capacity equivalent to the smallest drive.
A: You generally cannot change the RAID type of an existing storage pool without migrating data. Synology offers options like creating a new storage pool with a different RAID type and moving data, or using SHR which allows easier expansion and potential upgrades over time.
A: SHR: 2 drives. RAID 1: 2 drives. RAID 5: 3 drives. RAID 6: 4 drives. RAID 10: 4 drives (must be an even number).
A: This calculator provides an estimate based on standard RAID formulas. Actual usable space may be slightly less due to file system formatting (e.g., Btrfs, ext4), DSM overhead, and potential small differences in reported vs. actual drive capacity.
A: RAID 6 guarantees tolerance against failure of any two drives in the array. SHR can be configured to tolerate one drive failure (like RAID 5) or, if you have 4+ drives, it can be configured to tolerate two drive failures, similar to RAID 6, while still offering SHR's flexibility.