Best Practices for Recovering Data from a Failed NAS Promise Pegasus2 M4 RAID Configuration

Contents

• Why Regular Data Recovery Tools Can’t Restore Files from RAID
• Key Information About the NAS Promise Pegasus2 M4
• How to Remove Hard Disks from Your NAS and Connect Them to a PC
  • Step-by-Step Data Recovery with Hetman RAID Recovery
  • How to Safely Recover Data from Disk Images
  • Where Are the User’s Files Actually Stored?
  • RAID Recovery Software: Detailed Comparison

Why Regular Data Recovery Tools Can’t Restore Files from RAID

Conventional hard drives store user data by writing it sequentially across the disk surface, which means an entire file is typically located on a single drive. In contrast, when data is written to a RAID array, each file is split into multiple fragments. These fragments are then distributed and written in sequence across all the drives in the array. Depending on the configuration, fragment sizes can range from 2 KB to 2 MB, so every file is physically stored across several disks at once.

This approach significantly increases read and write performance — after all, writing two halves of a 1 GB file to two drives simultaneously is much faster than writing the full 1 GB to a single disk. However, this same mechanism makes file recovery far more complex.

Different RAID levels use different methods to distribute and protect data. On top of that, manufacturers like Promise often add their own proprietary structures and variations. As a result, data can be written to disks in many different formats, and each requires a specific approach during recovery.

How can storage tiering or caching strategies impact data availability and potential loss on NAS Promise Pegasus2 M4 devices?

Storage tiering and caching strategies can have a significant impact on data availability and potential loss on NAS Promise Pegasus2 M4 devices. Here are a few ways in which these strategies can affect data availability and potential loss:

1. Improved Performance: By implementing storage tiering and caching strategies, you can improve the overall performance of your NAS device. Caching allows frequently accessed data to be stored in faster storage media, such as solid-state drives (SSDs), resulting in faster read and write speeds. This improves data availability by reducing latency and ensuring quick access to frequently accessed data.
2. Data Redundancy: Storage tiering can also help in ensuring data redundancy. By using a combination of different storage media, such as SSDs and hard disk drives (HDDs), you can create redundant copies of critical data. In the event of a drive failure, the redundant copy can be used to maintain data availability and prevent potential loss.
3. Data Protection: Caching strategies, such as write-back caching or write-through caching, can impact data protection. Write-back caching temporarily stores write operations in cache before writing them to the permanent storage. While this improves performance, there is a risk of potential data loss if a power outage or system failure occurs before the data is written to the permanent storage. On the other hand, write-through caching immediately writes data to the permanent storage, ensuring data durability but potentially affecting performance.
4. Capacity Optimization: Storage tiering helps optimize storage capacity by automatically moving less frequently accessed data to slower storage tiers. This frees up space on faster storage media for frequently accessed data, improving performance. However, there is a risk of potential data loss if the tiering algorithm is not properly configured or if there is a failure in the tiering process.
5. Backup and Recovery: Storage tiering and caching strategies should be considered in the context of backup and recovery. While these strategies can improve performance and data availability, they should not be considered a substitute for regular backups. It is essential to have a robust backup strategy in place to protect against potential data loss caused by hardware failures, software errors, or other unforeseen events.

In summary, storage tiering and caching strategies can have a positive impact on data availability and performance on NAS Promise Pegasus2 M4 devices. However, careful planning, configuration, and monitoring are necessary to mitigate the potential risks of data loss and ensure the overall reliability and resilience of the storage system.

How to Remove Hard Disks from Your NAS and Connect Them to a PC

Although the NAS Pegasus2 M4 can be accessed over the network, you still need to remove its hard disks and connect them directly to a Windows PC. Only then can the recovery software properly scan and analyze the drives. Follow these steps:

1. Power off the NAS and disconnect it from the power source.

   WARNING! Before removing any drives, carefully read the device manual. Improper actions may damage both the NAS enclosure and the hard disks in the RAID array.

2. Remove the hard disks one by one, gently sliding each drive out of its slot. Remember that hard disks are highly sensitive: any impact or drop can cause serious physical damage.

3. Label each hard disk according to its position inside the NAS. The order of the drives is crucial for correct RAID reconstruction.

4. Connect the drives to your computer. In this video, we explain which ports you can use to connect hard disks and what to do if your PC does not have enough free connectors.

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   How to Order Remote Data Recovery

Step-by-Step Data Recovery with Hetman RAID Recovery

This program restores data from damaged RAID arrays and is fully compatible with Promise Pegasus2 M4. Each hard disk in the array contains technical metadata describing how files were written. When launched, Hetman RAID Recovery analyzes this metadata, automatically reconstructs the damaged array, and provides access to its contents. After that, you can browse the recovered disk and save your files. The program can also restore files that were accidentally deleted from the network drive.

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How to recover data from a Promise

Pegasus2 M4 has 4 HDD slots, and it supports the following array types:

• RAID 0;
• RAID 1;
• RAID 1E;
• RAID 3;
• RAID 5;
• RAID 6;
• RAID 30;
• RAID 50;
• RAID 60;
• JBOD;

NAS supports:

• exFAT, VFAT, FAT 12 / 16 / 32;
• NTFS / ReFS;
• APFS / HFS+;
• Ext2 / 3 / 4 / ReiserFS / XFS / UFS / ZFS / Btrfs;
• VMFS / HikvisionFS;

How to Safely Recover Data from Disk Images

This utility allows you to create a complete copy of a disk and work with the disk image instead of the physical drive. This approach helps protect your data from:

• Overwriting during the recovery process;
• Additional data loss caused by bad sectors;
• User errors.

To create a disk image, follow these steps:

1. Ensure you have enough free space to store the image. Its size will typically match the size of the original disk.

2. In the main window, select the target disk and choose Tools - Save Disk. You can also select multiple disks if needed.

3. When the Image Creation Wizard opens, select whether you want to save the entire disk or only a specific region. Adjust the settings and click Next.

   

4. Choose the directory where the image will be saved. You may select any available disk connected to your PC or upload the image via FTP.

   

Where Are the User’s Files Actually Stored?

The Promise Pegasus2 M4 network-attached storage keeps OS Linux operating system files on a separate RAID 1 (mirrored) array. Usually, all NAS systems create several volumes on every hard disk, and the first of them takes up to 2 Gb of space. This is where operating system files are stored. Other volumes are united into a RAID array where user’s data is written.

RAID Recovery Software: Detailed Comparison