Best Practices for Data Recovery from a NAS Promise Vess 1740i RAID Array Failure

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 a NAS Promise Vess 1740i device's cache settings impact data loss risks?

The cache settings on a NAS Promise Vess 1740i device can impact data loss risks in the following ways:

1. Write Cache: The write cache is used to temporarily store data before it is written to the underlying storage disks. Enabling write cache can improve write performance, but it also introduces a risk of data loss in case of power failure or system crash. If the write cache is not flushed to the disks before such events occur, the data in the cache may be lost.
2. Read Cache: The read cache stores frequently accessed data to improve read performance. While read cache does not directly impact data loss risks, it may affect data integrity if the cache becomes inconsistent with the underlying disks. If the NAS device experiences disk failures or data corruption, the read cache may serve outdated or corrupted data, leading to potential data loss or data inconsistency.
3. Battery Backup Unit (BBU): Some NAS devices, including the Promise Vess 1740i, offer a BBU to protect the write cache. In case of power failure, the BBU provides temporary power to flush the write cache to the disks, ensuring data integrity. Enabling the BBU can significantly reduce the risk of data loss related to the write cache.
4. Cache Synchronization: The NAS device may have settings to control the synchronization between cache and disks. It is crucial to ensure that the cache is synchronized with the disks to minimize the risk of data loss. If the synchronization is not performed regularly or properly, data inconsistencies or loss can occur.

To mitigate data loss risks, it is recommended to:

• Enable the BBU if available to protect the write cache.
• Regularly backup critical data to an external storage device or off-site location.
• Monitor the health of the storage disks and RAID arrays to detect and address any potential issues promptly.
• Implement a reliable power supply and backup power solutions to minimize power-related risks.
• Regularly update the NAS firmware and drivers to ensure bug fixes and security patches are applied.
• Follow best practices and manufacturer guidelines for cache settings and synchronization to maintain data integrity.

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

Although NAS Vess 1740i 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 Vess 1740i. 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

Vess 1740i has 16 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;

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 Vess 1740i 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