NAS, short for Network-Attached Storage, is a file-level storage device providing data access via the network. Although a typical NAS consists of several disks, it looks like a single logical storage when connected to, say, a home network. The so-called RAID technology is responsible for how drives combine into a single room. Without going into technical details, you can imagine that contents of the files are distributed evenly across NAS disks rather than written contiguously on the disks one by one.
Additionally, the so-called redundant configurations are used which allow recreating file content should the main copy of file data lost. QNAP, NETGEAR, Synology, and Buffalo are the most known NAS vendors offering NAS storage solutions both for home and for business.
If it happens that your NAS has failed, and you cannot get access to the data stored in it, the only DIY approach you can try is to recover data using software. There’s only one small catch – regular data recovery software can’t do this. To find out the reason behind it, let’s compare how data store on a NAS and a typical hard drive.
Typical Hard Drive
Let’s assume that a drive is formatted to the NTFS filesystem and there are several files stored on it. Closer to the beginning of the disk, there is an area with filesystem metadata where the records describing the locations of all the files are stored.
To retrieve data from a typical hard drive, the data recovery tools use two approaches or a combination of them. The first approach is to parse filesystem metadata so that to know where the file contents are located and how data are grouped into the folders. The advantage of such an approach is that you get the recovered data as it was originally stored, that is a structured folder tree and the original file names.
Also Read: How To Choose An iPhone Data Recovery Software.
The disadvantage of data recovery tools is the return result might be incomplete depending on the level of damage. It happens because the metadata is damaged. For example, if the metadata record of the file #2 is damaged (pointer from metadata to the file #2 content is lost), you cannot recover this file, although its content is still on the disk.
Within the second approach, filesystem metadata is not considered at all. The data recovery software searches the drive for the file content instead. It should be noted that, on the one hand, this approach works only with non-fragmented files, and on the other hand, only for those file types which a particular data recovery tool knows.
Naturally, there is no chance to recover the folder tree. Only file names can be recovered in a very limited set of cases.
More powerful data recovery tools use the combination of the approaches to extract as much data as possible.
NAS Disk Set
Unlike a typical drive where only one level of storing data – filesystem level – is used, a NAS operates with two levels:
- a level of RAID at which several disks are combined into a single storage,
- a filesystem level at which files are stored.
First, let’s look at how physical disks combine into a single virtual storage.
As you see, a virtual storage consists of blocks from different drives evenly included into a pool of storage space.
Now let’s illustrate how files store on the virtual volume.
It’s easy to see that the contents of the file #1 and files #2 are stored on the different physical disks (different color blocks). As for the filesystem, it doesn’t know on which disks the file content is stored since the filesystem works at the level of the virtual contiguous volume and is not even aware of the underlying level at which drives are combined.
So if you need to recover data from a NAS, using regular data recovery software like Recuva, or PC Inspector is impractical since such tools, on the one hand, cannot work with disk sets and therefore “solve” two-level configurations. And on the other hand, such tools can’t work with Linux filesystems which are widely used in NASes.
If you still launch, say Recuva, on a NAS disk, it can create the illusion of recovery since searching for known file types (for example .jpg) can bring something but it would be just file fragments rather than full files.
To recover data from a NAS, you should use special NAS recovery software like Home NAS Recovery, ReclaiMe, or Runtime data recovery, which can solve the overall task. When choosing the software, you need to take into account many criteria like filesystems supported.
For example, if you have an NETGEAR NAS, most likely you deal with BTRFS filesystem; in case of a QNAP device, this is ext; if you are an owner of a Buffalo NAS, look for the XFS filesystem support.
Additionally, you should find out whether the software can recreate a virtual NAS volume – some software can only read NAS metadata while others can recover the configuration.
No matter how good the NAS recovery software is, the best solution is still…to have a backup because none software can recover overwritten data as well as data from the “dead” drives.