RAID 50 Explained

5 min readJun 23, 2023

Image by PITS Global Data Recovery Services

In the previous blog, we discussed RAID 10, a data storage solution that offers performance, redundancy, and space efficiency. While RAID 10 is suitable for many scenarios, there are situations where it is not. In such cases, RAID 50 comes into play as an alternative and better solution.

This article will talk about RAID Level 50, explaining its functionality and how it addresses certain limitations.

What is RAID 50?

RAID, or Redundant Array of Independent Disks, is a technology that treats multiple disks as a single logical unit, providing improved performance, redundancy, and fault tolerance.

RAID 50 is a data storage technology that builds upon the principles of RAID, particularly RAID 5 and RAID 0, while incorporating an additional level of redundancy and fault tolerance. Like RAID 5, RAID 50 utilizes multiple drives and requires a minimum of four disks to implement. However, RAID 50 combines multiple RAID 5 arrays to create a larger logical unit with enhanced performance and resilience.

RAID 50 finds extensive use in various storage systems, including servers, network-attached storage (NAS) devices, and enterprise storage arrays. It is especially well-suited for applications that demand high data redundancy, fault tolerance, and performance. Consequently, RAID 50 is popular in environments where data protection and availability are critical, such as data centers, enterprise-level storage solutions, and large-scale file servers. Additionally, RAID 50 proves advantageous for applications involving substantial data volumes, such as video editing, multimedia storage, and database servers, where data loss or downtime can have severe consequences.

Structure

A RAID 50 array comprises four or more disks. Similar to RAID 5, data is divided into blocks and striped across the drives within each RAID 5 subarray. However, unlike RAID 5, RAID 50 combines multiple RAID 5 subarrays (typically three or more) into a larger unit. This structure combines the benefits of striping for performance and redundancy for fault tolerance.

The RAID 50 configuration provides an optimal balance between performance and fault tolerance. By distributing data across multiple drives, read and write operations can be executed concurrently, resulting in improved performance. Moreover, the use of multiple RAID 5 subarrays ensures that the failure of a single drive within a subarray does not lead to data loss. However, if drives fail in different subarrays, the array can sustain multiple simultaneous drive failures thanks to the distributed parity information.

Space Efficiency

The usable capacity of a RAID 50 array can be calculated using the following formula:

U = (N — P) * S

U — Usable capacity
N — Number of all disks
P— Number of disks reserved for parity
S — Size of the smallest disk

For example, in a RAID 50 array with six disks, each with a capacity of 2 TB (6 x 2 TB), and using one disk per RAID 5 subarray for parity, the usable capacity would be 8 TB.

Redundancy and Fault Tolerance

RAID 50 provides robust fault tolerance through the combination of multiple RAID 5 subarrays. Each RAID 5 subarray can tolerate the failure of a single drive without data loss. Consequently, the RAID 50 array as a whole can withstand the failure of multiple drives, as long as they are distributed across different subarrays.

This multi-level redundancy makes RAID 50 highly resilient against drive failures and ensures data availability. However, it is vital to promptly replace any failed drives and maintain the integrity of the entire array to minimize the risk of data loss.

Performance and Capacity

RAID 50 strikes a balance between performance and capacity, leveraging the advantages of striping and redundancy. By striping data across multiple drives within each RAID 5 subarray, read and write operations can be parallelized, resulting in improved performance compared to a single RAID 5 array.

The capacity of a RAID 50 array depends on the total capacity of all the drives minus the number of drives reserved for parity. RAID 50 offers efficient capacity utilization, allowing for larger usable storage compared to RAID 1 (mirroring) or RAID 10 (striping and mirroring). However, similar to RAID 5, write operations may incur a slight penalty due to the need to calculate and write parity information.

Write Penalty and Rebuild Time

The write penalty in RAID 50 refers to the additional time required to calculate and write parity information during write operations. This can impact overall write performance compared to RAID levels without parity, such as RAID 0. The write penalty becomes more noticeable during random write operations since each write operation involves updating the corresponding data block and the associated parity information. However, dedicated hardware RAID controllers or optimized software implementations can help mitigate the write penalty.

Rebuilding a failed drive in a RAID 50 array can be time-consuming, particularly for larger-capacity drives (e.g., 20 TB or more). During the rebuild process, data from the remaining drives and the distributed parity information are used to reconstruct the missing data on the new drive. The rebuild time depends on factors such as drive size, array load during the rebuild, and overall system performance. It is essential to have a backup strategy in place and closely monitor the rebuild process to ensure data integrity and availability.

Pros of RAID 50

Offers a higher level of fault tolerance compared to single RAID 5 arrays, capable of withstanding the failure of multiple drives distributed across different subarrays.
Efficient use of storage capacity, combining the benefits of striping and redundancy.
Improved data protection against simultaneous drive failures by leveraging distributed parity information.

Cons of RAID 50

Write performance can be slightly impacted due to the need to calculate parity.
Rebuilding an array after drive failures can be time-consuming and resource-intensive.
If multiple drives fail or develop bad sectors during the rebuild process, data loss may occur.

Conclusion

RAID 50 provides an advanced level of fault tolerance, making it an excellent choice for applications that require high data protection and resilience against multiple drive failures. By combining multiple RAID 5 subarrays, RAID 50 enhances the reliability of the array, ensuring data integrity and availability. It strikes a balance between performance and capacity, enabling efficient storage utilization.