How to recover data from malfunctioning NAS units
NAS Fundamentals
NAS, or Network Attached Storage, is a data storage solution easily connectable to a PC network.
NAS units typically lack a keyboard or monitor, solely providing file-based data storage services.
These devices can be constructed using dedicated chips, similar to hardware RAID,
or by utilizing Linux operating system drivers installed on a computer.
As NAS uses a regular RAID for data storage, it is susceptible to failures typical of RAIDs.
However, the course of action in the event of NAS failure resulting from a storage system issue varies
based on the type of NAS implementation.
Recovering NAS Using Dedicated Hardware
In some instances, NAS operates using a dedicated chip and its firmware rather than a customized Linux system.
Although this type of NAS was nearly extinct by the end of 2010,
the following information is provided for comprehensive understanding.
One approach is to swap drives with an identical device. Caution is necessary with RAID 5 arrays,
as there is a risk that the controller might not recognize the disks and initiate initialization, resulting in data loss.
Alternatively, RAID recovery software capable of reconstructing RAID configurations can be employed.
In such cases, connecting member disks to any PC with sufficient ports and initiating RAID recovery software,
like ReclaiMe Free RAID Recovery , is required.
Recovering NAS Based on Linux/mdraid
Many contemporary NAS units, such as those produced by QNAP, Synology, or Netgear, essentially function as specialized PCs.
These units utilize an Intel Atom or similar CPU and a customized Linux installation to manage the RAID.
Although some components like SATA hot-swap backplanes and indicator LED arrays may not be standard in a regular PC,
the overall system closely resembles one. Smaller-scale NAS units may employ a system-on-chip design, ARM, or PPC processor,
all controlled by Linux.
The choice of Linux as the operating system enables vendors to quickly and inexpensively provide a feature-rich system
by leveraging existing Linux software. The RAID types used in a Linux-based NAS unit typically involve ext3 or ext4
for the filesystem and standard md-raid drivers for RAID capability.
Since standard software is used, connecting NAS disks to any Linux system is usually straightforward.
Once connected to a Linux PC, the command "sudo mdadm --assemble --scan --assume-clean" can be used to explore the NAS data.
However, using disks outside the NAS may pose challenges,
as vendors do not optimize storage systems for compatibility with regular PC Linux.
In such cases, data recovery may be necessary to access the data, even if the RAID itself is intact.
If Linux fails to provide useful results, an alternative option is data recovery software designed to process mdraid records.
While Linux reads only correct metadata, data recovery software handles damaged data.
Examples include ReclaiMe data recovery software , which can automatically recover NAS data.