NAS QNAP HS-251 RAID Arrays: Mechanical and Logical Failures Recovery Guide

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 QNAP 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 the number of concurrent users or clients accessing a NAS QNAP HS-251 device affect data loss risks?

The number of concurrent users or clients accessing a NAS (Network Attached Storage) device like QNAP HS-251 can potentially affect data loss risks in the following ways:

1. Increased risk of accidental deletion: With more users accessing the NAS device simultaneously, the chances of accidental file deletion or modification may increase. A user might unintentionally delete or overwrite important data, leading to data loss.
2. Higher probability of file conflicts: When multiple users are simultaneously modifying the same file, conflicts can arise. If proper file versioning and conflict resolution mechanisms are not in place, it may result in data loss or corruption.
3. Performance impact: A large number of concurrent users accessing the NAS device can put a strain on its resources, such as CPU, memory, and network bandwidth. This increased load may lead to degraded performance, which can increase the likelihood of data loss due to timeouts, network errors, or system crashes.
4. Security vulnerabilities: More concurrent users mean a larger attack surface and increased potential for security breaches. If the NAS device is not properly secured or user access controls are not adequately implemented, unauthorized access or malicious activities by one user can compromise the data of other users, leading to data loss or theft.
5. Backup and recovery challenges: Managing backups and ensuring data recovery becomes more complex with an increased number of concurrent users. Coordinating and scheduling regular backups, verifying their integrity, and restoring data accurately can be more challenging when multiple users are actively using the NAS device.

To mitigate these risks, it is important to implement proper access controls, user permissions, and file versioning mechanisms. Regular backups should be performed and tested to ensure data can be restored in case of any data loss event. Additionally, educating users about best practices for data management and security can help minimize the risks associated with concurrent access.

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

Although NAS HS-251 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 QNAP HS-251. 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 QNAP

HS-251 has 2 HDD slots, and it supports the following array types:

• RAID 1;

NAS supports:

• ZFS;
• EXT4;
• EXT3;
• exFAT;
• FAT32 (External Disk Only);
• NTFS (External Disk Only);
• HFS+ (External Disk Read Only);

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 QNAP HS-251 network-attached storage keeps QTS (QuTS hero) 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