How to recover data from Digiever DS-16336-RM Pro+ NAS

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 Digiever 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 Digiever DS-16336-RM Pro+ device's caching policy impact data loss risks?

The caching policy of a NAS (Network Attached Storage) device like the Digiever DS-16336-RM Pro+ can impact data loss risks in several ways:

1. Write caching: NAS devices often use write caching to improve performance by temporarily storing write operations in cache memory before writing them to the underlying storage media. However, if power is suddenly lost or the system crashes before the cached data is written, there is a risk of data loss. To mitigate this risk, NAS devices usually have mechanisms like battery-backed cache or write-through caching, which ensure that data is written to the storage media before acknowledging the completion of a write operation.
2. Read caching: Read caching is used to improve read performance by storing frequently accessed data in cache memory. While read caching generally doesn't pose a significant risk of data loss, there is a possibility of data inconsistency if the cached data is outdated or becomes corrupted. NAS devices often employ techniques like cache coherence protocols or periodic cache refreshing to minimize this risk.
3. Cache synchronization: In NAS devices with multiple nodes or clustered configurations, cache synchronization becomes critical. If data modifications are made on one node and not immediately synchronized with the caches of other nodes, there is a risk of data inconsistency or loss during a failover or system recovery. NAS devices typically employ cache coherency protocols, like write-back or write-through mechanisms, to ensure data consistency across nodes.
4. Cache failure: Like any other hardware component, cache memory can also fail. If the cache memory of a NAS device fails, it may result in data loss or data corruption. To mitigate this risk, NAS devices often have redundant cache modules or mechanisms for cache mirroring, where data is simultaneously stored in multiple cache modules to ensure data availability even in case of cache failure.

It is important to note that while caching policies can impact the risk of data loss, they are just one aspect of a comprehensive data protection strategy. Other factors like RAID configurations, backup practices, and disaster recovery plans should also be considered to minimize the risk of data loss in a NAS device.

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

Although NAS DS-16336-RM Pro+ 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 Digiever DS-16336-RM Pro+. 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 Digiever

DS-16336-RM Pro+ has 16 HDD slots, and it supports the following array types:

• RAID 0;
• RAID 1;
• RAID 5;
• RAID 6;
• 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 Digiever DS-16336-RM Pro+ 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