RAID Recovery™
Recovers all types of corrupted RAID arrays
Recovers all types of corrupted RAID arrays
Last updated: Jan 05, 2024

How to Recover Data from RAID on Linux

Welcome to our comprehensive guide on "How to Recover Data from RAID on Linux." RAID systems, known for their redundancy and enhanced performance capabilities, are a popular choice in many computing environments. However, data loss in RAID systems can pose a significant challenge. What do you do when faced with such a scenario?

This article is designed to cater to both novices and experienced Linux users, offering a detailed roadmap for recovering data from various RAID configurations. We begin by introducing you to the basic principles of RAID technology and then delve into the common causes of data loss in RAID systems. Our focus will be on providing effective recovery strategies that are tailored to different types of RAID setups, including RAID 0, RAID 1, RAID 5, and more intricate configurations.

Throughout the guide, we emphasize practical solutions that leverage Linux-based tools and methods. We'll guide you step-by-step through the process, ensuring you gain a deep understanding of both the theory and practice of RAID data recovery.

By the end of this guide, you'll have a robust understanding of how to navigate through RAID data recovery processes using Linux. We aim to equip you with the skills and confidence needed to effectively address and overcome data loss issues in RAID systems. Let's embark on this journey into the realm of RAID data recovery on Linux, and transform you into a capable handler of RAID-related data challenges.

What Is Linux (mdadm)

Linux mdadm is a utility for managing and monitoring software RAID devices on Linux systems. RAID, which stands for Redundant Array of Independent Disks, is a technology that combines multiple disk drives into a single logical unit for the purposes of data redundancy, performance improvement, or both.

Here are some key aspects of mdadm:

  • Software RAID Management: mdadm is used to create, manage, and monitor software RAID arrays. Unlike hardware RAID, which uses dedicated hardware to manage the RAID array, software RAID relies on the operating system to handle these tasks.
  • Support for Various RAID Levels: It supports multiple RAID levels, including RAID 0 (striping), RAID 1 (mirroring), RAID 5 (striped with parity), RAID 6 (striped with double parity), and RAID 10 (nested or hybrid). Each level offers different balances of performance, storage capacity, and data safety.
  • Array Creation and Management: mdadm can be used to assemble RAID arrays, add new drives to an existing array, remove drives, or move arrays to different systems. It is also used for replacing failed drives and managing spare drives.
  • Monitoring and Reporting: The tool provides capabilities for monitoring the health and status of RAID arrays. It can alert users to failures or issues with the RAID arrays, which is crucial for preventing data loss and ensuring the integrity of the stored data.
  • Integration with Linux Kernels: mdadm is closely integrated with Linux kernels, making it a standard tool in many Linux distributions for managing RAID arrays.
  • Data Recovery: In the event of a drive failure or other issues, mdadm can be used to recover data from the RAID array, assuming the RAID level supports redundancy.
  • Flexibility and Accessibility: Being a command-line tool, mdadm offers great flexibility and control to users who are comfortable with terminal commands. It's widely used in Linux environments, especially in servers and systems where data integrity and performance are critical.

Tips Before RAID Recovery Using mdadm

Recovering data from a RAID array using mdadm on Linux can be a complex process, and it's essential to take some precautions and preparatory steps to maximize the chances of successful recovery. Here are some important tips to consider before attempting RAID recovery with mdadm:

  • Do Not Write to the Affected Array: Avoid writing any new data to the RAID array once you suspect data loss or array failure. Writing new data can overwrite the lost data and make recovery more difficult or impossible.
  • Backup Existing Data: If possible, make a complete backup of the RAID array before beginning the recovery process. This step is crucial to prevent data loss if something goes wrong during the recovery process.
  • Check Drive Health: Inspect the health of the individual drives in the RAID array. Use tools like smartctl to check for hardware issues on the drives. Replace any failing drives before proceeding with the recovery.
  • Document Current Configuration: Take note of the current RAID configuration, including RAID level, disk order, and any other relevant settings. This information is crucial for the recovery process.
  • Use a Live Linux Environment: Consider running a live Linux environment from a USB or CD to perform the recovery. This approach ensures that the system's normal operations do not interfere with the recovery process.
  • Prepare Necessary Tools: Ensure that you have mdadm and other potentially necessary tools installed and ready to use. You might also need data recovery tools in case mdadm cannot fully recover the data.
  • Familiarize Yourself with mdadm Commands: Before starting the recovery, familiarize yourself with the relevant mdadm commands and options. Misusing these commands can lead to further data loss.
  • Seek Professional Help if Unsure: If you're not confident in your ability to recover the data or if the data is extremely critical, consider seeking help from a professional data recovery service.
  • Avoid RAID Reinitialization: Do not reinitialize or recreate the RAID array as this can destroy the data.
  • Keep System Stable: Ensure that the system is stable and there are no power issues. A UPS (Uninterruptible Power Supply) is recommended to avoid power disruptions during the recovery process.
  • Document the Recovery Process: Keep a detailed record of all the steps you take during the recovery process. This documentation can be invaluable if you need to seek further assistance.

By following these tips, you can improve the chances of successful data recovery using mdadm on a Linux system. RAID recovery can be challenging, and taking the proper precautions is essential to protect your data.

Limitations of mdadm

mdadm is a powerful tool for managing and monitoring software RAID arrays on Linux systems, but it also has certain limitations. Understanding these limitations is crucial for users who rely on mdadm for RAID management and recovery. Here are some of the key limitations:

  • Software RAID Performance: Since mdadm manages software RAID, it utilizes the system's CPU for RAID operations. This can result in lower performance compared to hardware RAID solutions, especially for high-throughput or computationally intensive tasks.
  • Complexity for Beginners: mdadm is a command-line based tool, which can be complex and intimidating for users who are not familiar with Linux command-line interfaces. This complexity can lead to user errors, especially in critical operations like RAID recovery.
  • Dependency on System Stability: Being a software solution, mdadm's performance and reliability are dependent on the underlying system's stability. Issues with the Linux system can affect the RAID array's performance and reliability.
  • No Hardware Failure Protection: Unlike hardware RAID controllers, mdadm does not provide protection against hardware failures like a broken motherboard or a power supply issue. In such cases, the entire RAID array might become inaccessible.
  • Limited Support for Advanced Features: Some advanced RAID features available in dedicated RAID controllers, like battery-backed cache or hardware encryption, are not available or are limited in mdadm.
  • Recovery Limitations: While mdadm can handle some common RAID failure scenarios, it may not be effective in complex data loss situations, especially where there are simultaneous multiple drive failures in certain RAID configurations like RAID 0.
  • Drive Compatibility Issues: mdadm might face compatibility issues with drives that use proprietary or non-standard firmware, often seen in drives designed for specific hardware RAID controllers.
  • No Automatic Failover or Hot Swapping: Software RAID setups managed by mdadm typically do not support automatic failover or hot swapping of failed drives, features often found in hardware RAID setups.
  • Risk of Data Loss Due to Misconfiguration: Incorrectly using mdadm commands can lead to misconfiguration and potential data loss, especially if the user is not familiar with RAID concepts and mdadm command syntax.
  • Dependence on Disk Health: The effectiveness of mdadm in managing a RAID array is heavily dependent on the health of the individual disks. Bad sectors or failing drives can significantly impact the performance and reliability of the RAID array.

While mdadm is a powerful and flexible tool for managing software RAID arrays, these limitations should be considered when choosing a RAID solution and during RAID array management and recovery processes.

How to recover data on Linux-based RAID Using mdadm

Recover RAID Using mdadm

Recovering a RAID array using mdadm in Linux is a multi-step process that requires a careful approach to prevent further data loss. Here’s a general outline of the steps you would typically follow. Please note that the specific steps can vary depending on the RAID level (e.g., RAID 0, RAID 1, RAID 5, etc.) and the nature of the problem.

1. Assess the Situation

  • Identify the Problem: Determine what caused the RAID failure. It could be a failed disk, a corrupt RAID configuration, or other hardware issues.
  • Check Disk Health: Use tools like smartctl to check the health of each drive in the RAID array.

2. Backup Data

  • If possible, make a complete backup of all the drives in the RAID array before attempting any repair.

3. Install and Prepare mdadm

  • Ensure mdadm is installed on your system. You can install it via your distribution's package manager (e.g., sudo apt-get install mdadm for Debian/Ubuntu).
  • Stop the RAID array if it is running, using mdadm --stop /dev/mdX, where X is your RAID device number.

4. Reassemble the RAID Array

  • Attempt to reassemble the array using mdadm --assemble --scan. This command tries to assemble the RAID array using the information from the mdadm.conf file and the metadata on the disks.
  • If automatic assembly doesn't work, you may need to assemble the array manually. This involves explicitly specifying the devices: mdadm --assemble /dev/mdX /dev/sd[a1] /dev/sd[a2] ..., replacing X with your RAID device number and a1, a2, etc., with the appropriate partition identifiers.

5. Assess RAID Array Status

  • Check the status of the RAID array using cat /proc/mdstat or mdadm --detail /dev/mdX.
  • Look for any discrepancies or failures in the array.

6. Repair the RAID Array

  • If a disk is faulty, you may need to replace it. Add the new disk using mdadm --manage /dev/mdX --add /dev/sdY, where Y is the new disk.
  • If the array is degraded but functional, you may be able to rebuild it using the existing disks.

7. Monitor the Rebuild Process

  • Monitor the progress of the rebuild using cat /proc/mdstat or mdadm --detail /dev/mdX. The rebuild process can take a long time, especially for large arrays.

8. Verify Data Integrity

  • Once the rebuild is complete, verify the integrity of the data on the RAID array.
  • Run filesystem checks if necessary.

9. Update mdadm Configuration

  • Ensure the mdadm.conf file is updated with the current RAID array configuration.

Important Considerations

  • RAID Level Specifics: The recovery process can vary significantly depending on the RAID level.
  • Data Safety: Always prioritize the safety of your data. If the data is critical, consider consulting with a data recovery professional.
  • Documentation: Keep a record of all the steps and commands you execute for future reference.

Recover Linux-based RAID Using the mdadm Alternative

DiskInternals RAID Recovery Software

DiskInternals RAID Recovery is a software tool designed to recover data from RAID arrays that have encountered issues such as disk failures or array misconfigurations. It's suitable for both hardware and software RAIDs and supports various RAID configurations. Here's a general guide on how to use DiskInternals RAID Recovery:

Pre-Recovery Steps

  • Assess the Situation: Determine the nature of the RAID problem you're facing. This will help you decide on the appropriate recovery method.
  • Stop Using the Affected RAID: Avoid writing new data to the RAID array to prevent overwriting lost data.
  • Backup Data: If possible, create an image of the RAID disks for safety before attempting recovery.

Installing DiskInternals RAID Recovery

  1. 1. Download and Install: Download the RAID Recovery software, and follow the installation instructions.
  2. 2. Launch the Software: Open the DiskInternals RAID Recovery tool.

Recovery Process

  1. 1. RAID Reconstruction:

  • The software can automatically detect the RAID type. If it's unable to detect, you can manually specify the RAID type (RAID 0, RAID 1, RAID 5, etc.).
  • If disks are out of order, manually arrange them in the correct order based on your RAID configuration.
  1. 2. Scanning for Lost Data:

  • Choose between a fast scan or a full (deep) scan. The full scan is more thorough but takes longer.
  • The software will scan the disks for recoverable files.
  1. 3. Preview and Recovery:

  • After the scan, you can preview the recoverable files.
  • Select the files or folders you want to recover.
  1. 4. Saving Recovered Data:

  • Choose a safe location to save the recovered data. It's essential not to save the data back to the RAID array being recovered.
  • You may need to purchase a license to save the recovered files, as the free version typically allows only previewing the recoverable files.

Additional Features

  • File Systems Supported: DiskInternals RAID Recovery supports various file systems, including NTFS, FAT, HFS, EXT2/3/4, and others.
  • RAID Controller Support: The software can work with RAIDs controlled by popular RAID controllers.
  • Creating Disk Images: For safety, you can create a disk image of the RAID for recovery, reducing the risk to the original disks.


  • Read Documentation: Review the software's documentation for specific instructions and tips.
  • Technical Support: If you encounter difficulties, consider reaching out to DiskInternals' technical support for assistance.


In conclusion, RAID (Redundant Array of Independent Disks) systems, while offering benefits in terms of data redundancy and performance, can be subject to data loss due to various reasons such as disk failure, array misconfiguration, or other hardware issues. Recovering data from a RAID setup, especially on Linux systems, requires a careful and knowledgeable approach.

The mdadm tool in Linux is a powerful utility for managing and recovering software RAID arrays. It offers flexibility and control for those familiar with Linux command-line interfaces, but its complexity and reliance on system stability and user expertise can be challenging. Before attempting recovery with mdadm, it's crucial to take preventive steps like backing up data, carefully documenting the RAID configuration, and ensuring all disks are healthy. The recovery process involves reassembling the RAID array, repairing or replacing faulty disks, and verifying data integrity. However, this process has its limitations and risks, particularly for complex RAID levels or severe data loss scenarios.

For those seeking a more user-friendly and less technical approach, software solutions like DiskInternals RAID Recovery provide an alternative. This software supports a range of RAID configurations and file systems, offering automated processes for RAID reconstruction and data recovery, including options for deep scanning and file preview. It's a valuable tool for users who are not comfortable with manual, command-line recovery methods, though it may require purchasing a license for full data recovery capabilities.

Regardless of the method chosen, RAID data recovery should be approached with caution. Data safety is paramount, and if the RAID contains critical data, it may be prudent to seek professional data recovery services. These services can offer expertise and resources that go beyond what typical software solutions provide, potentially offering a higher chance of successful recovery for particularly complex or severe cases.

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