Best Practices for Recovering Data from NAS Promise Pegasus R4 RAID Array Failures

Contents

• Why can’t ordinary software tools restore files from RAID?
• How to take hard disks out of the NAS and connect them to a PC?
  • Restoring data with Hetman RAID Recovery
  • Safe recovery from disk images
  • Where are user’s files stored?
  • Comparison of software for RAID recovery

Why can’t ordinary software tools restore files from RAID?

Conventional hard disks keep user’s data by writing it to their surface in a consecutive way, and this is how an entire file is stored on a single hard disk. However, when data is written to a RAID system, a file is divided into several parts. Then these parts are written consecutively to all hard disks within such array. The size of such parts may range from 2 KB to 2 MB, so each file is stored on several hard disks at the same time.

Such approach helps to speed up read and write operations, and it is evident that saving two parts of a file having the size of 1 GB to two hard disks simultaneously is much faster than saving the same 1 GB of data to one hard disk. However, this peculiarity makes file recovery more complicated.

Various RAID levels store information in different ways. Additionally, manufacturers like Promise also introduce some modifications to this process, and that is why data can be written to hard disk in a wide variety of ways.

How can regular data verification or checksum processes help maintain data integrity on NAS Promise Pegasus R4 devices?

Regular data verification or checksum processes can help maintain data integrity on NAS Promise Pegasus R4 devices in the following ways:

1. Detecting and preventing data corruption: Regular data verification processes involve comparing the checksum of the data being read with the stored checksum value. If the checksums don't match, it indicates that data corruption has occurred. By performing these verifications regularly, you can identify corrupted data early and take appropriate actions to prevent further damage.
2. Ensuring accurate data storage: Checksum processes generate a unique value based on the data being stored. This value is stored alongside the data. When retrieving the data, the checksum is recalculated and compared with the stored value. If they match, it ensures that the data has been accurately stored and retrieved without any modifications.
3. Identifying hardware or software issues: Regular data verification processes can help identify any underlying hardware or software issues that may be causing data corruption. If you consistently encounter checksum mismatches, it may indicate problems with the storage device, cables, or even the NAS system itself. By addressing these issues promptly, you can prevent further data integrity problems.
4. Preventing silent data corruption: Silent data corruption refers to the situation where data gets corrupted without any indication or error message. By regularly performing data verification or checksum processes, you can proactively identify silent data corruption and take corrective measures before it leads to data loss or other critical issues.
5. Enhancing data recovery capabilities: In case of data loss or corruption, having regular data verification processes in place can improve the chances of successful data recovery. By comparing the checksums of the corrupted data with the known good checksums, you can identify which portions of the data are corrupted and attempt to recover them from backups or other sources.

Overall, regular data verification or checksum processes provide an additional layer of protection and help ensure the integrity of data stored on NAS Promise Pegasus R4 devices.

How to take hard disks out of the NAS and connect them to a PC?

Although NAS Pegasus R4 can be accessed over the network, you still need to take the hard disks out of the storage device and connect them to a Windows computer. Only in this case will the software be able to scan them properly. Here is what you should do:

1. Turn off the storage and disconnect it from the power supply.

   WARNING! Before you start taking hard disks out of your NAS device, read the manual carefully. Incorrect actions may damage your network-attached storage and/or the hard disks within the RAID system.

2. Take the hard disks out of the NAS one by one, carefully removing them from their slots. Remember that the disks are extremely vulnerable: hitting or dropping them may result in serious physical damage.

3. Make sure to mark each hard disk in accordance with how they were installed inside the NAS.

4. Remove the hard disks and connect them to the computer. In this video, we have explored what ports are used to connect hard disks, and what to do if there are not enough ports or connectors.

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   How to Order Remote Data Recovery

Restoring data with Hetman RAID Recovery

This program recovers data from damaged RAID arrays and is fully compatible with Promise Pegasus R4. The hard disks that make up the RAID contain technical information about the algorithm used to save files. When launched, Hetman RAID Recovery reads this information and puts the damaged array together. Then you can open the disk and save your files. Also, you can recover the files accidentally deleted from the network drive.

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How to recover data from a Promise

Pegasus R4 has 4 HDD slots, and it supports the following array types:

• RAID 0;
• RAID 1;
• RAID 1E;
• RAID 3;
• RAID 5;
• RAID 6;
• JBOD;

NAS supports:

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

Safe recovery from disk images

This utility lets you save an entire copy of the disk to file and then work with this image instead of the actual disk. Such feature helps to protect data on the disk from:

• Overwriting during the recovery process;
• Loss resulting from bad sectors;
• User mistakes.

To create an image, do the following:

1. Make sure that you have enough free space to save the image. The image file size usually equals the disk size.

2. Select the disk in the main window, and choose from the menu Tools – Save Disk. You can select multiple disks to be saved.

3. When the image creation wizard starts, you can choose to save the entire disk or select only a part of it. Specify the parameters and click Next.

   

4. At this stage, you need to choose a directory where to save the image. Choose any disk connected to this PC, or save the image by FTP.

   

Where are user’s files stored?

The Promise Pegasus R4 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.

Comparison of software for RAID recovery