What is NAS? A Network Attached Storage (NAS) is a server device that provides data storage services over a local area network (LAN). Such devices offer various file sharing services, such as Windows file sharing (CIFS, SMB), Apple File Sharing (AFS), etc.

Devices of this type store files in so-called "shared folders", accessible from "client" devices over a LAN.

There are plenty of different NAS devices from different vendors: from simple "LAN disk" boxes with very simple system-on-chip (SOC) hardware and up to big corporate class storage systems, built on powerful server hardware.

NAS devices implement a variety of storage technologies as well: from standard file systems and RAID (redundant arrays of independent disks) to different vendor-specific extensions for enabling reliable data storage and keeping data safe.

What are the reasons for data loss from a NAS? The most common reason for any incident is a human mistake: from "oops, I've deleted the wrong folder!" and to "have you tested that device firmware update?". Other reasons include force-majeure factors and natural hardware degradation.

These are the most typical causes for data loss from a network attached storage:

• Data deletion by mistake (such as selecting the wrong folder);
• Single or multiple drives failure;
• Failed NAS firmware update (due to an internal error, storage failure or power outage);
• Different problems during changing storage configuration: changing volume size, adding or replacing disks in a RAID, etc.;
• Hardware damage due to floods, electrical shock, overheat etc.

If data loss has happened, the most sensible advice is to turn the device off and contact your local data recovery service company. But as data recovery services are usually quite expensive, another option one should consider is using a piece of special data recovery software. Among major advantages of employing this type of tools are:

• Much lower price;
• Guaranteed confidentiality of sensitive personal or corporate data;
• Data can be retrieved in shorter terms;
• Most data recovery companies already utilize the same software.

However, self-service data recovery has its disadvantages:

• At least basic technical skills are required to operate with hardware internals (hard disks, adaptors, connectors, etc.);
• Lack of experience may lead to fatal mistakes;
• Wrong evaluation of hardware state may make things worse (such as additional damage to the surface of the failed disk).

It is not recommended to do self-service data recovery from failed disks (those which have bad blocks or other hardware issues). If hard disk drives or the NAS device itself work properly, it might make sense to consider self-service data recovery.

What are the difficulties of data recovery from a NAS? Some NAS devices are built on x86-compatible hardware and allow for data recovery performed in the conventional way: you may boot this device using Linux Live CD or Live Flash drive, run conventional data recovery software for Linux OS, find lost data and copy it to some removable media or to a network shared folder.

What about simple system-on-chip devices? They often run a reduced Linux operating system as well, however, due to hardware incompatibility (these devices often use processors of the ARM family) or limited resources they are not able to run conventional data recovery software and require either employing very specific software or removing disks from the NAS, connecting them to a PC and running conventional data recovery software. The latter method is the only option in the cases when NAS hardware is "dead".

On the other hand, a simple one- or two-disk NAS may have very solid design and require performing a very complicated procedure of hard disk removal. So, running special NAS recovery software without disk removal may be the only option for self-service data recovery and avoiding NAS destruction.