What is WD My Cloud Home NAS?
My Cloud Home is a network-attached personal storage solution from Western Digital. It serves as a central location for saving and backing up digital content from the user’s mobile devices, Windows or Mac computers, that can be accessed remotely through Internet connection using a web browser or a special application.
Launched in 2017, it was meant to be an addition to the company’s famous WD My Cloud line. However, as an entry-level device, it does not have the same advanced file sharing and networking functionality as compared to the majority of fully fledged NAS units from Western Digital or any other popular brand. At the same time, it is very compact in size, straightforward to set up and is perfectly suitable for users who are just getting started with networked storage. It is also sometimes described as a hybrid between an external hard drive and an actual NAS.
My Cloud Home is available in both single-drive and dual-drive configurations, with various capacities up to 8 or 20 TB respectively. The two-bay variant, My Cloud Home Duo, provides a second drive to which the data can be mirrored automatically using the traditional RAID 1 scheme. Thus, if one of the drives fails, a copy of the data will be still present on the other.
All appliances come pre-installed with the WD’s proprietary operating system, which initially ran on the basis of Android but was eventually migrated to the Linux platform. The storage is partitioned based on GPT, and most partitions are formatted with the Linux ext4 file system.
What is peculiar about a WD My Cloud Home volume?
The simple nature of the device doesn’t exclude its underlying technical complexity. A deeper look at its insides shows that My Cloud Home has a non-standard approach to organizing data. The files in it are stored with automatically generated names and directory structure, which makes it quite difficult to read from the drives removed from the original My Cloud Home unit.
As a rule, the internal drive of My Cloud Home comprises a big number of partitions (24+). Most of them perform service functions, whereas the largest one is particularly interesting, as it contains all the user’s data. Though it makes use of the Linux's native ext4 file system, in this case, its content may not look as familiar as expected.
The files in it are typically located in the "root/restsdk/data/files/" directory. The latter consists of multiple subdirectories arranged in an alphabetic order (from 0 to 9 and from A to Z). The files in them have random technical identifiers rather than human-readable names. The key to all of the above is a special SQLite database which is used to determine logical file paths.
The database itself is stored as the "index.db" file in the "root/restsdk/data/db" directory. The "FILES" table in it records all the information about the data on the disk. This table includes a unique ID for each file in the file system, its technical name (ContentID), as well as the real name defined by the user. Moreover, each file has a "ParentID" attribute which locates it in a directory structure.
The aforementioned SQLite database is essential to determine the original names, extensions and directories for all the user’s files. If it gets lost or corrupted, it becomes impossible to map them
to the normal layout obtained via the standard WD My Cloud Home app or web browser.
The described technology is supported for data recovery and access by the following software products: