Synology Storage Calculator & Guide


Synology Storage Calculator

Determine the ideal storage capacity and RAID configuration for your Synology NAS. Input your needs to get started!

Synology Storage Needs Calculator



How many GB of new data do you expect to add each day?


How many days of data do you need to keep accessible?


Choose your desired level of fault tolerance. SHR is Synology’s flexible RAID implementation.


Enter the capacity of each individual hard drive you plan to use (e.g., 8TB, 16TB).


How many drive bays will your Synology NAS have (or how many drives will you initially install)?


Storage Efficiency by RAID Type

RAID Type / Redundancy Usable Capacity Formula (relative to raw) Example Drive Count Usable Capacity (with 8TB drives, 4 drives) Storage Efficiency
Single Disk / None N * Capacity 1 8 TB 100%
RAID 1 / SHR-1 (1-disk redundancy) (N-1) * Capacity / 2 2 8 TB 50%
RAID 5 / SHR-2 (2-disk redundancy) (N-1) * Capacity 3 16 TB 66.7% (for N=4)
RAID 6 / SHR-3 (3-disk redundancy) (N-2) * Capacity 4 16 TB 50% (for N=4)
Table 1: RAID configuration efficiency comparison. Usable capacity depends heavily on the number of drives (N) and their individual capacity. SHR dynamically adjusts efficiency based on drive count.

Projected Storage Growth Over Time

Chart 1: Visual representation of projected storage consumption based on daily growth and retention period.

What is Synology Storage Planning?

Definition and Purpose

Synology storage planning involves calculating the necessary storage capacity and choosing the appropriate RAID (Redundant Array of Independent Disks) configuration for a Synology Network Attached Storage (NAS) device. This process ensures that your NAS can adequately store your data, provide the desired level of data protection against drive failures, and accommodate future data growth. Effective Synology storage planning is crucial for both home users managing media libraries and photos, and businesses requiring reliable data backup and access.

Who Should Use a Synology Storage Calculator?

Anyone planning to purchase or expand a Synology NAS setup should utilize a Synology storage calculator. This includes:

  • Home Users: Consolidating media (movies, music, photos), backing up computers and mobile devices, running Plex servers.
  • Small Businesses: Centralizing file storage, implementing backup solutions for workstations, hosting small applications or databases, managing surveillance footage.
  • Power Users: Anyone who needs significant local storage with redundancy and performance benefits offered by NAS solutions.

Common Misconceptions

Several misconceptions surround Synology storage planning:

  • “More drives always mean more usable space”: Incorrect. While more drives can increase total raw capacity, RAID configurations use some capacity for redundancy. The efficiency decreases with higher redundancy levels (e.g., RAID 6 vs RAID 5).
  • “RAID protects against everything”: False. RAID protects against hard drive failures, not against accidental deletion, file corruption, malware, natural disasters, or theft. A comprehensive backup strategy is still essential.
  • “Any hard drive works”: Not always. Synology recommends specific NAS-grade drives for reliability and compatibility. Using desktop drives may lead to unexpected issues or reduced performance.
  • “Storage calculators are overly complex”: While the underlying technology can be complex, user-friendly calculators simplify the process, focusing on key inputs like daily growth and redundancy needs.

Synology Storage Calculation Formula and Mathematical Explanation

The core of Synology storage calculation involves determining the total data volume needed over a specific period and then ensuring that the chosen RAID configuration can provide this usable space while offering the desired protection.

Step-by-Step Derivation

  1. Calculate Total Data Volume Needed: This is the raw amount of data you expect to store.

    Total Data Volume = Daily Data Growth (GB) * Data Retention Period (Days)
  2. Determine Usable Capacity Provided by Configuration: This depends on the RAID type, number of drives, and individual drive capacity.

    For RAID 1 / SHR-1 (N drives): Usable Capacity = (N - 1) * Individual Drive Capacity / 2

    For RAID 5 / SHR-2 (N drives): Usable Capacity = (N - 1) * Individual Drive Capacity (assuming parity uses space equivalent to one drive)

    For RAID 6 / SHR-3 (N drives): Usable Capacity = (N - 2) * Individual Drive Capacity (assuming parity uses space equivalent to two drives)

    Synology’s SHR (Synology Hybrid RAID) is more flexible, especially with mixed drive sizes, but for simplicity in calculation, SHR-1 approximates RAID 1 efficiency and SHR-2 approximates RAID 5 efficiency when drives are of similar size. The calculator aims to find a configuration that meets or exceeds the `Total Data Volume`.
  3. Calculate Minimum Required Raw Capacity: The calculator must find the smallest total raw capacity (sum of all drive capacities) that can provide at least the `Total Data Volume` after RAID overhead.

    Let Required Raw Capacity = Total Data Volume (GB)

    The calculator then determines the minimum number of drives and their capacity such that (Total Drives * Drive Capacity) >= Required Raw Capacity AND the resulting usable space from the chosen RAID level is sufficient. Often, the calculator suggests a minimum number of drives that allows the chosen RAID level to function and then calculates the total raw capacity needed.

Variable Explanations

Here’s a breakdown of the variables used in the calculation:

Variable Meaning Unit Typical Range
Daily Data Growth The average amount of new data added per day. GB 1 GB – 100+ GB (highly variable)
Data Retention Period The duration for which data must be stored and accessible. Days 30 Days – ∞ (often 365 days or more)
Redundancy Level The number of drive failures the RAID array can tolerate.

0 = No Redundancy

1 = 1-Disk Redundancy (e.g., RAID 1, SHR-1)

2 = 2-Disk Redundancy (e.g., RAID 5, SHR-2)

3 = 3-Disk Redundancy (e.g., RAID 6, SHR-3)		 Integer 0, 1, 2, 3
Individual Drive Capacity The storage size of a single physical hard drive. TB 2 TB – 24+ TB
Number of Drives The total number of physical hard drives in the NAS. Count 1 – 16+ (depending on NAS model)
Total Data Volume Needed The total storage space required for all data over the retention period. GB Calculated
Usable Capacity The actual storage space available to the user after RAID overhead. TB Calculated
Total Raw Capacity The sum of the capacities of all drives installed. TB Calculated
Required Drives for Configuration Minimum drives needed to implement chosen RAID level with sufficient capacity. Count Calculated
Total Capacity (Primary Result) The recommended minimum *raw* storage capacity for the NAS. TB Calculated

Practical Examples (Real-World Use Cases)

Example 1: Home Media Server & Backup

Scenario: A user wants to consolidate their movie collection, store family photos, and back up two laptops. They anticipate adding about 15 GB of photos and downloaded media daily. They want to keep data for at least 2 years (730 days) and prefer the protection of 1-disk redundancy (like SHR-1 or RAID 1).

Inputs:

  • Estimated Daily Data Growth: 15 GB
  • Data Retention Period: 730 Days
  • Redundancy Level: 1 (1-disk redundancy)
  • Individual Drive Capacity: 10 TB
  • Number of Drives: 4

Calculation & Results:

  • Total Data Volume Needed = 15 GB/day * 730 days = 10,950 GB = 10.95 TB
  • With 4 drives and 1-disk redundancy, the usable capacity formula (simplified for calculation) is roughly (4-1)*10TB / 2 = 15 TB.
  • The calculator determines that 10.95 TB of usable space is needed. A 4-bay NAS with 10TB drives in a 1-disk redundant configuration provides ~15TB usable.
  • Primary Result: 40 TB (Total Raw Capacity: 4 x 10 TB)
  • Intermediate Values: Usable Capacity per Drive: ~5 TB (approx. half of one drive, due to RAID 1), Total Raw Capacity: 40 TB, Required Drives for Configuration: 4 (to achieve ~15TB usable with redundancy).

Interpretation: The user needs approximately 11 TB of usable storage. A 4-bay NAS populated with 10 TB drives offers significantly more usable space (around 15 TB) than strictly required, providing room for future growth. The total raw capacity investment is 40 TB.

Example 2: Small Business File Server & Surveillance

Scenario: A small office (5 employees) uses their NAS for shared project files and storing CCTV footage. Daily file additions average 30 GB, and they need to retain CCTV footage for 30 days. They require high data protection due to business-critical files, opting for 2-disk redundancy (SHR-2 or RAID 6).

Inputs:

  • Estimated Daily Data Growth: 30 GB
  • Data Retention Period: 30 Days
  • Redundancy Level: 2 (2-disk redundancy)
  • Individual Drive Capacity: 16 TB
  • Number of Drives: 5

Calculation & Results:

  • Total Data Volume Needed = 30 GB/day * 30 days = 900 GB = 0.9 TB
  • With 5 drives and 2-disk redundancy (RAID 6), usable capacity is (5-2)*16TB = 48 TB.
  • The calculator finds that 0.9 TB usable is needed. A 5-bay NAS with 16 TB drives in a RAID 6 configuration provides 48 TB usable.
  • Primary Result: 80 TB (Total Raw Capacity: 5 x 16 TB)
  • Intermediate Values: Usable Capacity per Drive: ~16 TB (approx. (N-2)*Capacity / N), Total Raw Capacity: 80 TB, Required Drives for Configuration: 4 (minimum required for RAID 6, but 5 drives are used for higher capacity).

Interpretation: The business needs minimal usable storage (less than 1 TB) for the specified retention period. However, the requirement for 2-disk redundancy and the use of 16 TB drives in a 5-bay NAS result in a very large usable capacity (~48 TB) and a significant total raw capacity investment (80 TB). This setup provides substantial room for future growth and very high data protection. It highlights that redundancy and drive size can significantly impact the overall investment, even when daily needs are small. A smaller NAS or fewer/smaller drives might suffice if future growth is minimal, but this setup prioritizes safety and scalability.

How to Use This Synology Storage Calculator

Using the Synology Storage Calculator is straightforward. Follow these steps to estimate your storage needs:

  1. Estimate Daily Data Growth: Determine how much new data (photos, videos, documents, backups, surveillance footage) you add on an average day. Be realistic; it’s better to slightly overestimate than underestimate.
  2. Define Data Retention Period: Specify how long you need to keep this data. For backups, this might be 30-90 days. For media archives or sensitive business data, it could be years.
  3. Choose Redundancy Level: This is critical for data protection.
    • None: No protection against drive failure. Only suitable for non-critical data or temporary storage.
    • 1-Disk Redundancy (SHR-1/RAID 1): Protects against a single drive failure. Requires at least 2 drives.
    • 2-Disk Redundancy (SHR-2/RAID 5): Protects against two simultaneous drive failures. Requires at least 3 drives. Recommended for critical data.
    • 3-Disk Redundancy (SHR-3/RAID 6): Protects against three simultaneous drive failures. Requires at least 4 drives. Maximum protection.
  4. Input Individual Drive Capacity: Enter the storage capacity (in Terabytes, TB) of the hard drives you intend to use. Ensure all drives are the same size for optimal RAID performance and simplicity, although Synology Hybrid RAID (SHR) offers flexibility with mixed sizes.
  5. Specify Number of Drives: Enter the total number of drive bays in your Synology NAS or the number of drives you plan to install initially.
  6. Click ‘Calculate’: The calculator will process your inputs.

How to Read Results

  • Primary Result (Total Capacity): This is the recommended *total raw storage capacity* you should aim for in your NAS, considering your inputs. It represents the sum of all drive capacities needed to meet your usable storage goals with the selected RAID level.
  • Usable Capacity per Drive: This indicates roughly how much storage capacity each drive effectively contributes to the usable pool after accounting for RAID overhead and redundancy.
  • Total Raw Capacity: The sum of the capacities of all the drives you would install.
  • Required Drives for Configuration: The minimum number of drives needed to implement your chosen RAID level. The calculator ensures your specified number of drives is sufficient.
  • Formula Explanation: Provides a summary of the logic used.

Decision-Making Guidance

Use the results to make informed decisions:

  • Purchasing Hardware: If the calculated ‘Total Capacity’ requires more drives or larger drives than your intended NAS model supports, you may need to reconsider your NAS model or adjust your storage requirements/retention period.
  • RAID Level Choice: Balance data protection needs against usable storage space. Higher redundancy means less usable space from the same set of drives.
  • Future Proofing: The calculator helps you plan for growth. If your calculated needs are close to the limits of your planned setup, consider choosing larger drives or a NAS with more drive bays from the outset.

Key Factors That Affect Synology Storage Results

Several factors influence the outcome of your Synology storage calculations and the overall effectiveness of your setup:

  1. Data Growth Rate: This is arguably the most significant factor. A rapidly growing data set will necessitate larger capacity sooner. Underestimating this can lead to running out of space quickly. Accurately predicting future needs is key.
  2. Data Retention Policies: Strict compliance requirements or long-term archiving needs drastically increase the required storage volume. A policy to keep data for 7 years, for example, will need substantially more space than a 30-day retention period.
  3. RAID Configuration (Redundancy Level): Each level of redundancy consumes storage space. RAID 1 (1-disk redundancy) uses 50% of raw capacity, while RAID 6 (2-disk redundancy) uses 66-75%. Choosing higher redundancy sacrifices usable space but increases resilience. Synology Hybrid RAID (SHR) offers more flexibility, especially with mixed drive sizes, but the fundamental trade-off remains.
  4. Drive Capacity and Quantity: The size of individual drives directly impacts how many drives are needed for a target capacity. Using larger drives can reduce the number of drives required, potentially saving space in the NAS chassis, but also means a single drive failure represents a larger proportion of your total data. The number of drives is constrained by the NAS model’s drive bays.
  5. Type of Data Stored: Different data types have different growth patterns. Video files (like from surveillance cameras or high-resolution media) consume space much faster than documents or code repositories. This impacts the ‘Daily Data Growth’ estimate.
  6. Future Scalability Needs: Planning for future expansion is crucial. Will you need to store significantly more data in 2-3 years? Choosing a NAS with more drive bays than initially needed, or planning to upgrade to larger drives later, ensures the system can grow with your requirements without a complete overhaul.
  7. File System Overhead: While not explicitly in basic calculators, file systems (like Btrfs or ext4 used by Synology) have their own overhead for metadata, snapshots, and internal management. Btrfs, with features like snapshots, can consume additional space.
  8. Data Deduplication and Compression: Some advanced storage solutions and file systems offer data deduplication or compression. If enabled, these features can reduce the *effective* storage needed, but they come with CPU overhead and aren’t always suitable for all data types. Synology DSM has limited options for this at the file system level.

Frequently Asked Questions (FAQ)

What is the difference between SHR and traditional RAID?
Synology Hybrid RAID (SHR) is Synology’s automated RAID management system. It allows for greater flexibility, particularly when using drives of different sizes. For example, in an SHR array with two 4TB drives and one 8TB drive, SHR utilizes the 4TB drives fully and adds the 8TB drive, providing more usable space than a traditional RAID 1 or RAID 5 would allow in that mixed-drive scenario. Traditional RAID (RAID 0, 1, 5, 6, 10) requires drives of the same size for optimal performance and predictable capacity. SHR aims to maximize usable storage while providing redundancy.

Does RAID protect against data loss from accidental deletion or ransomware?
No. RAID protects against the physical failure of one or more hard drives. It does not protect against logical errors, accidental file deletion, file corruption, malware, viruses, or ransomware attacks. For comprehensive data protection, you must implement a separate backup strategy (e.g., backing up your NAS to another location, cloud storage, or another NAS). Synology’s snapshot feature (available with Btrfs file system) can help recover previous versions of files, mitigating some risks.

How often should I check my NAS drive health?
Synology DSM provides tools to monitor drive health using S.M.A.R.T. (Self-Monitoring, Analysis, and Reporting Technology) tests. It’s recommended to schedule regular S.M.A.R.T. tests (e.g., weekly or monthly) and to configure notifications within DSM to alert you immediately if any drive reports potential issues or errors. Prompt action can prevent data loss during a failure event.

Can I upgrade my storage capacity later?
Yes, Synology NAS devices generally support storage expansion. Depending on the model and RAID type (especially SHR), you can often achieve this by replacing existing drives with larger ones one by one, or by adding more drives if your NAS has empty bays. Synology provides detailed guides on how to perform these upgrades safely without data loss.

What is the difference between usable capacity and raw capacity?
Raw capacity is the total storage space of all the physical hard drives installed in the NAS added together (e.g., 4 x 8TB drives = 32TB raw capacity). Usable capacity is the actual storage space available to you after the RAID configuration has been set up, which reserves space for redundancy (parity data) and potentially system overhead. For example, a 4-bay NAS with 8TB drives in RAID 5 (1-disk redundancy) might offer around 24TB of usable capacity, not the full 32TB raw capacity.

Should I use NAS-specific drives or desktop drives?
It is strongly recommended to use NAS-specific drives (like Western Digital Red or Seagate IronWolf). These drives are designed for 24/7 operation, vibration tolerance in multi-drive environments, and often feature firmware optimized for NAS workloads. While desktop drives might work initially, they are not built for the constant demands of a NAS and may have lower reliability, shorter lifespans, and compatibility issues, potentially leading to data loss or system instability.

How does Synology’s snapshot technology impact storage usage?
Synology’s snapshot technology, available on the Btrfs file system, creates point-in-time copies of your data. These snapshots are efficient as they only store the blocks of data that have changed since the previous snapshot. However, they do consume additional storage space over time as more changes accumulate. The amount of space consumed depends on the frequency of snapshots and the rate of data modification.

Is it better to have fewer large drives or more smaller drives for the same total capacity?
This depends on your priorities. Fewer large drives can simplify management and potentially offer higher raw capacity per drive bay. However, with RAID configurations, a failure of a larger drive means losing more data temporarily until replacement and rebuild. More smaller drives, especially in a RAID setup with higher redundancy (like RAID 6), might offer better resilience against multiple drive failures occurring simultaneously, and the rebuild time after a single drive failure might be faster. For SHR, mixing drive sizes is also possible.


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