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Last updated: May 06, 2024

SHR - what is it? What is the difference between SHR and RAID Drives?

SHR (Synology Hybrid RAID) and RAID (Redundant Array of Independent Disks) are two pivotal technologies that often leave users deliberating on their best choice. This article aims to demystify these two storage methods, providing a clear understanding of each and highlighting their differences to aid users in making informed decisions.

SHR, developed by Synology, is tailored for their Network Attached Storage (NAS) systems, offering a flexible approach to managing storage with an emphasis on ease of use and efficient storage utilization, especially when dealing with hard drives of varying sizes. It simplifies the RAID configuration process and is designed to be more intuitive for users who may not have extensive technical expertise in RAID configurations.

On the other hand, RAID is a well-established data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both. RAID configurations are standardized by various levels (RAID 0, RAID 1, RAID 5, RAID 10, etc.), each offering different balances of performance, data availability, and storage capacity.

The core of this article will delve into the operational mechanisms of both SHR and traditional RAID, examining how they manage data redundancy, their ease of use, performance implications, scalability, and suitability for different use cases. By understanding these facets, users can discern which system aligns best with their storage needs, be it for personal use, small businesses, or larger enterprises.

Note: best RAID configuration tips!

What is Synology Hybrid RAID (SHR)?

Synology Hybrid RAID (SHR) is an automated RAID management system developed by Synology that is designed to simplify storage management and maximize data capacity while still providing data protection. It is particularly useful for users who are not familiar with the intricate details of various RAID configurations. SHR is exclusive to Synology NAS devices and offers several benefits, particularly when dealing with hard drives of different sizes.

Here's an overview of SHR's key features:

  • Flexibility with Mixed Drive Sizes: Unlike traditional RAID configurations, which typically require all drives to be of the same size to maximize storage efficiency, SHR allows users to combine drives of different sizes without wasting space. SHR automatically optimizes the storage capacity and redundancy based on the drives you have.
  • Easy Setup and Management: SHR is designed for ease of use, especially for users who may not have technical expertise. Setting up SHR is straightforward via Synology's DiskStation Manager (DSM) interface, making it accessible for home users or small businesses.
  • Data Protection: SHR provides one or two-disk redundancy, similar to RAID 1 or RAID 5/6, which means it can tolerate the failure of one or two drives (depending on the SHR type chosen) without data loss. This feature is critical for safeguarding data against hardware failures.
  • Expandability: With SHR, you can expand your storage capacity by replacing existing drives with larger ones one at a time. After each drive is replaced and the data is rebuilt onto the new drive, the total storage capacity will increase, which is not always possible with traditional RAID without reconfiguring the entire volume.
  • Efficiency: SHR maximizes the use of disk space across different drive sizes while ensuring data protection. It automatically calculates the best way to distribute data across the drives to make efficient use of available space.

In summary, SHR is tailored for users who require a reliable, efficient, and easy-to-manage RAID system without delving into the complexities of traditional RAID configurations. It is an ideal choice for Synology NAS users looking for a balance between data protection and optimal storage utilization.

How does SHR maximize storage capacity?

Synology Hybrid RAID (SHR) maximizes storage capacity by intelligently managing how data is distributed across drives of varying sizes, something that traditional RAID configurations do not do as effectively. Here's a detailed breakdown of how SHR accomplishes this:

  • Combining Different Drive Sizes: Traditional RAID configurations require that all drives be of the same size, or else the extra space on larger drives is wasted. For example, in a RAID 1 or RAID 5 setup, if you pair a 2TB drive with a 4TB drive, the system will only use 2TB from each drive, effectively ignoring the additional capacity of the larger drive. SHR, on the other hand, can utilize the full capacity of each drive, even when they are of different sizes.
  • Dynamic Allocation of Storage: SHR automatically and efficiently utilizes the total combined storage capacity of all drives in the array. When SHR is implemented, it divides each drive into smaller, more manageable partitions. Then, it combines these partitions across multiple drives to create volumes that maximize storage capacity and ensure redundancy.
  • Efficient Use of Space: For instance, if you have one 4TB drive and two 2TB drives in an SHR configuration, SHR will create a RAID 1 volume with the two 2TB drives and use the remaining space on the 4TB drive in conjunction with part of its own space to create another RAID 1-like protection, maximizing the use of all available space.
  • Storage Expansion: SHR also provides an easy and efficient way to expand storage capacity. If you replace one of the smaller drives in the array with a larger one, SHR allows the array to expand without wasting the additional space of the larger drive. Once all drives are of equal or greater size than the largest drive in the initial setup, the full capacity of all drives can be used.

By effectively managing and utilizing the storage space across drives of varying sizes, SHR maximizes storage capacity while still providing the necessary data protection and redundancy that users expect from a RAID configuration. This approach makes SHR particularly advantageous for users who may have a mix of drive sizes and wish to upgrade their storage capacity over time without wasting space.

How do I expand the storage capacity of SHR?

Expanding the storage capacity of a Synology Hybrid RAID (SHR) is straightforward and user-friendly, allowing you to increase your NAS storage as your data needs grow. Here is a step-by-step guide on how you can expand your SHR volume:

  • Verify the SHR Type: Before you start, ensure your SHR is configured for expansion. SHR without data protection (single-drive SHR) or SHR with 1-disk redundancy allows for expansion. Understanding your current SHR configuration is crucial for planning the expansion properly.
  • Back Up Your Data: Although SHR expansion is designed to be safe, it's always best practice to back up your important data before making any changes to the storage system to prevent any accidental data loss.
  • Replace Smaller Drives with Larger Ones: If your SHR volume is full and you want to expand the capacity, you can replace existing drives with larger ones. Here's how:
    • Power down your Synology NAS (if it does not support hot-swapping).
    • Replace one of the smaller drives with a larger one.
    • Power on the NAS and log in to DSM (DiskStation Manager).
    • The DSM will recognize that a drive was replaced and will prompt you to repair the SHR volume. During this repair, the data from the old drive will be rebuilt on the new, larger drive.
  • Repair the Volume: In DSM, go through the repair process, which will integrate the new drive into the volume and synchronize the data. This process can take several hours, depending on the size of your drives and the amount of data.
  • Repeat the Process if Necessary: If you have more than one drive that you want to replace, repeat the replacement process one drive at a time, allowing the SHR volume to repair completely between each new drive installation.
  • Expand the SHR Volume: Once all the new, larger drives are installed and the SHR volume has been repaired, you can expand the volume to utilize the additional space. In DSM, navigate to the storage manager and select the option to expand the volume. The system will then use the additional disk space, increasing your total storage capacity.
  • Verify the Expansion: After the expansion process is complete, check the storage capacity in DSM to ensure that the SHR volume reflects the new, larger capacity.

By following these steps, you can efficiently expand the storage capacity of your Synology Hybrid RAID without losing your existing data, providing a seamless and effective way to grow your storage space in line with your increasing data requirements.

Does SHR provide fault tolerance?

Yes, Synology Hybrid RAID (SHR) provides fault tolerance, which is a key feature for ensuring data integrity and continuity in the event of a hard drive failure. The level of fault tolerance depends on the specific SHR configuration you choose. Here's how SHR provides fault tolerance:

  • SHR with Single-Disk Redundancy: This is the most common SHR setup and is similar to RAID 5. It allows one drive to fail without any loss of data. In this configuration, the data is striped across all drives with parity information distributed among them. If a drive fails, the system can rebuild the lost data using the parity information from the remaining drives. Once you replace the failed drive with a new one, the system can restore the redundancy by rebuilding the data onto the new drive.
  • SHR-2 with Two-Disk Redundancy: This configuration is akin to RAID 6 and provides an additional layer of protection by allowing for two drives to fail simultaneously without data loss. It is particularly useful for larger arrays where the risk and impact of a second drive failing before the first failed drive is replaced and rebuilt are greater. SHR-2 uses a dual parity system, meaning it distributes two sets of parity data across all drives, enabling the system to recover from two concurrent drive failures.

The choice between SHR and SHR-2 depends on your specific needs for data protection, the number of drives in your NAS, and the criticality of your data. While SHR-2 offers higher fault tolerance, it also consumes more storage capacity for parity information, so it's essential to balance your need for data protection with your storage capacity requirements.

It's important to note that while SHR provides fault tolerance, it is not a substitute for regular backups. Even with SHR's redundancy, other catastrophic events like fire, theft, or multiple simultaneous drive failures beyond the redundancy level can still result in data loss. Therefore, maintaining offsite backups is crucial for comprehensive data protection.

What is RAID?

RAID (Redundant Array of Independent Disks) is a data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both. It was introduced in the late 1980s to improve storage reliability and performance over single-drive configurations. RAID can be implemented through either hardware or software, and it offers various levels, each designed for different use cases and offering different balances of performance, data availability, and storage capacity.

Here are some of the most common RAID levels:

  • RAID 0 (Striping): This level splits data evenly across two or more disks with no redundancy, offering improved performance but no fault tolerance. If one drive fails, all data on the RAID 0 array is lost.
  • RAID 1 (Mirroring): Data is copied identically from one drive to another, creating a "mirror." RAID 1 offers excellent fault tolerance (as all data is duplicated) but at the cost of halving the total storage capacity.
  • RAID 5 (Striped with Parity): This level requires at least three drives and distributes parity information along with the data across all drives. RAID 5 offers a good balance of performance, storage efficiency, and fault tolerance, allowing for the failure of one drive without data loss.
  • RAID 6 (Striped with Double Parity): Similar to RAID 5 but requires at least four drives and provides two parity blocks instead of one. This allows the array to survive the failure of two drives.
  • RAID 10 (or 1+0): This is a combination of RAID 1 and RAID 0 and requires a minimum of four drives. It provides the performance benefits of striping (RAID 0) along with the redundancy of mirroring (RAID 1). It's excellent for workloads that require high performance and fault tolerance.

Each RAID level has its specific use cases, benefits, and drawbacks. The choice of RAID level depends on the required balance between performance, capacity, and data protection. RAID helps to protect against data loss in the event of a drive failure, but like SHR, it is not a substitute for a comprehensive backup strategy. RAID configurations can also be more complex to manage than SHR, particularly when dealing with heterogeneous drive sizes or when planning for future expansion.

SHR vs Traditional RAID – Data Storage Mechanism and Capacity

Traditional RAID

Data Storage Mechanism:

Traditional RAID combines multiple physical disks into a single logical unit through hardware or software. The data is distributed across the disks in various ways, depending on the RAID level:

  • RAID 0 uses striping, where data is divided into blocks and each block is written to a separate disk drive. This enhances performance but offers no fault tolerance.
  • RAID 1 mirrors data across all disks, providing high fault tolerance but reducing the total storage capacity by half.
  • RAID 5 and RAID 6 use striping with parity, spreading data and parity information across all drives, allowing for data recovery in the event of a drive failure. RAID 5 supports one drive failure, whereas RAID 6 supports two.
  • RAID 10 combines the features of RAID 0 and RAID 1, offering both speed and redundancy by striping and mirroring data.


The storage capacity in traditional RAID depends on the RAID level and the size of the drives used. For example, in a RAID 1 setup, the total available storage is half of the combined drive capacity because of mirroring. In RAID 5, one drive's capacity is used for parity information, so the total available storage is the sum of the capacities of all drives minus one drive.

Synology Hybrid RAID

Data Storage Mechanism:

SHR is an automated RAID management system that allows for mixing drives of unequal sizes without wasting storage space. It is exclusive to Synology NAS devices and operates by creating an optimized storage layout that adapts to the mix of drive sizes:

  • SHR effectively utilizes the total storage capacity by combining the smaller partitions from larger drives with full partitions from smaller drives, ensuring all space is used efficiently. It offers fault tolerance similar to RAID 5.
  • SHR-2 provides an additional layer of redundancy, similar to RAID 6, tolerating the failure of two drives without data loss.


SHR maximizes the usable storage capacity when using drives of different sizes. For example, in a system with one 4TB drive and two 2TB drives, traditional RAID would limit the storage capacity to match the smallest drive, treating all as 2TB drives. SHR, however, would allow for more of the 4TB drive to be used, increasing the overall storage capacity of the array. When drives are replaced with larger ones over time, SHR can also expand its volume to utilize the additional space, which is not always possible or as straightforward with traditional RAID configurations.

In summary, while traditional RAID offers well-established methods for configuring data redundancy and performance, SHR provides a more flexible and storage-efficient approach, particularly beneficial for environments with mixed drive sizes or where ease of storage management and maximization are priorities.

Synology Hybrid RAID vs RAID

When comparing Synology Hybrid RAID (SHR) and traditional RAID configurations, it's essential to understand the key distinctions that may influence the choice between them based on the specific needs and contexts of users:

Flexibility and Ease of Use:

  • SHR: Designed with user-friendliness in mind, SHR is particularly advantageous for those who may not have extensive knowledge of RAID configurations. It allows for the use of drives of varying sizes without wasting storage space, automatically optimizing and managing the array for you.
  • Traditional RAID: Requires a more manual setup and a better understanding of each RAID level's implications. It usually does not support mixing drives of different sizes without losing storage capacity on the larger drives.

Storage Efficiency:

  • SHR: Maximizes storage efficiency, especially when using disks of different capacities. It can combine smaller partitions from larger drives with full partitions from smaller drives to utilize all available space.
  • Traditional RAID: Generally less storage-efficient when using disks of varying sizes, as it will limit the storage capacity to the smallest disk in the array for certain RAID levels (e.g., RAID 1, 5, 10).

Fault Tolerance:

  • SHR and Traditional RAID: Both offer fault tolerance, but the level of protection depends on the specific SHR or RAID configuration. SHR provides one or two-disk redundancy (similar to RAID 5/6), while traditional RAID levels offer various fault tolerance mechanisms, ranging from none (RAID 0) to two-disk redundancy (RAID 6).


  • SHR: Offers excellent scalability, allowing users to replace existing drives with larger ones gradually and expand the volume without reconfiguring the entire system.
  • Traditional RAID: Typically requires more planning for future expansion. Expanding or changing the array often involves backing up data, rebuilding the array, and restoring the data.


  • SHR: While SHR offers simplicity and efficiency, its performance can be slightly lower than traditional RAID configurations due to its dynamic management and optimization processes.
  • Traditional RAID: Offers predictable performance characteristics based on the chosen RAID level. For example, RAID 0 is optimized for performance, whereas RAID 1 focuses on redundancy.


  • SHR: Best suited for home users or small businesses using Synology NAS systems that require a straightforward, flexible storage solution with efficient use of mixed drive sizes.
  • Traditional RAID: More appropriate for environments where specific RAID configurations are needed for performance or redundancy requirements, and where the storage system can be adequately managed and maintained.

Comparison table: SHR and RAID (Advantages & Disadvantages)

FeatureSHR AdvantagesSHR DisadvantagesTraditional RAID AdvantagesTraditional RAID Disadvantages
FlexibilityCan mix drives of different sizes without wasting space.Limited to Synology NAS systems.Fixed configurations can be optimized for specific needs.Cannot mix drive sizes without losing storage capacity.
Ease of UseAutomated setup and management, user-friendly for non-experts.Less customizable in terms of RAID configurations.Highly customizable configurations.Requires more technical knowledge to setup and manage.
Storage EfficiencyMaximizes usable storage, especially with mixed drive sizes.Slightly less efficient than traditional RAID if all drives are of equal size and a specific RAID level is desired.Fixed RAID levels may offer better efficiency for arrays with identical drive sizes.Efficiency decreases if using mixed drive sizes, leading to wasted space.
Fault ToleranceOffers 1 or 2-disk redundancy (similar to RAID 5/6).Two-disk redundancy (SHR-2) consumes more storage space.Various levels of fault tolerance, including options without redundancy for maximum performance.Higher RAID levels (like RAID 6) that offer more fault tolerance also consume more storage space.
ScalabilityEasy to expand by replacing drives with larger ones over time.Expansion is still limited by the need to replace one drive at a time and rebuild the array.Some RAID levels can be expanded, though often more complex and time-consuming.Expanding or changing the array often requires full backup and restore, especially for RAID levels without inherent expandability.
PerformanceGenerally offers good performance, but can be slightly lower due to the overhead of managing mixed drive sizes.Performance may not be as high as a perfectly tuned traditional RAID array.RAID levels can be specifically chosen to optimize performance.Performance can be significantly compromised in certain configurations, like RAID 1 or 6.
SuitabilityIdeal for home users and small businesses looking for ease of use and storage efficiency.Not suitable for environments where Synology NAS is not used or where granular control over RAID configuration is needed.Suitable for enterprise environments or when specific RAID configurations are required for performance or redundancy.Not ideal for scenarios where ease of use and automatic management are prefe

RAID vs SHR – Which Is Better?

Deciding whether RAID or Synology Hybrid RAID (SHR) is better depends on the user's specific needs, technical expertise, and the context in which the storage solution will be deployed. Here's a breakdown of considerations to help determine which might be better in various scenarios:

For Home Users and Small Businesses:

  • SHR: Generally better for home users and small businesses that may not have dedicated IT staff. Its ease of use, flexibility with mixed drive sizes, and automated management make it an ideal choice for those who need an efficient, straightforward storage solution without a deep dive into technical details.
  • RAID: Could be overkill in terms of complexity for standard home use but might be the right choice for small businesses with specific performance or configuration requirements that SHR cannot meet.

For Data Enthusiasts and Tech-Savvy Users:

  • SHR: Offers a good balance of simplicity and efficiency, especially appealing if the user prefers a set-it-and-forget-it approach but still wants some level of data protection and efficiency.
  • RAID: Better for those who enjoy fine-tuning their system to optimize performance and data redundancy based on their exact specifications. Tech-savvy users might prefer RAID for its transparency and control over the data protection level and performance.

For Mixed-Drive Environments:

  • SHR: Clearly advantageous if you have hard drives of varying sizes and want to maximize the total storage capacity without wasting any space.
  • RAID: Not ideal for mixed-drive environments unless you are comfortable with some level of storage inefficiency or plan to use identical drives for optimal efficiency.

For Enterprise Environments:

  • SHR: Might not be the best fit for large enterprise environments that require highly specific RAID configurations for performance and data redundancy, given SHR's limitations in customization and its exclusive availability on Synology NAS systems.
  • RAID: Typically preferred in enterprise settings due to its standardization, predictability, and wide range of configuration options that can be tailored to specific enterprise needs, including high availability, performance, and fault tolerance.

In Summary:

  • Choose SHR if: You value ease of use, have mixed drive sizes, or prefer automated management without needing granular control over RAID configurations.
  • Choose RAID if: You require specific RAID configurations for performance or redundancy, have uniform drive sizes, or need a storage solution that adheres to enterprise-grade requirements.
Tip: data recovery from RAID


In conclusion, the decision between Synology Hybrid RAID (SHR) and traditional RAID hinges on the user's specific requirements, technical comfort level, and the operational environment of the storage solution. SHR stands out for its user-friendliness, flexibility with mixed drive sizes, and efficient storage utilization, making it an excellent choice for home users, small businesses, or anyone utilizing Synology NAS systems who seeks a balance between ease of use and effective data protection.

On the other hand, traditional RAID configurations offer a broader spectrum of options that can be fine-tuned for specific performance, capacity, and redundancy needs. They cater well to environments where users possess the technical acumen to manage RAID levels or where enterprise-grade data requirements necessitate precise control over storage configurations.

For users with mixed drive sizes or those seeking straightforward storage solutions with decent fault tolerance, SHR provides an advantageous approach. Conversely, for those in need of rigorous, customized storage solutions — especially in enterprise settings where performance and data redundancy are critical — traditional RAID configurations remain the gold standard.

Ultimately, both SHR and traditional RAID have their place in data storage strategies. The choice between them should be informed by the user's specific needs, the technical environment, and the level of control and customization required. By carefully considering these factors, users can select the storage solution that best aligns with their data management goals and operational context.


  • Is SHR faster than RAID 5?

    SHR typically exhibits slower performance relative to RAID 0 and RAID 1 configurations. Nonetheless, it delivers speed comparable to that of RAID 5 and RAID 6 setups.

  • How does SHR work with 2 drives?

    Conversely, SHR enables the expansion of a storage pool immediately after upgrading two drives, facilitating the formation of a redundant storage array. To extend an SHR configured for two-drive fault tolerance (SHR-2), the additional storage becomes accessible once you either incorporate more drives or enlarge the existing ones.

  • What is the best RAID for Synology?

    RAID 5 is highly recommended for NAS deployment as it offers an optimal mix of performance and redundancy. It necessitates at least three drives, with one drive dedicated to storing parity information essential for reconstructing the array's data in the event of a drive failure.

  • Is SHR the same as RAID 1?

    SHR exhibits lower performance relative to RAID 0 and RAID 1 configurations, yet it provides comparable speed to that observed in RAID 5 and RAID 6 setups.

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