Folders and files on network storage with ext4 file system disappeared, how to recover?

Question

linux

Hey!
A small company has a network storage in the form of WD my cloud ex2. It acted as a shared folder, inside which the files of the organization were located. Each department put documents in their own folders (pdf, doc, xls, jpg).
Everything worked to this day without interruption, until at one moment the phone rang from alarmed users: “We can’t find such a folder, although it was there half an hour ago.” The first thought was that they simply moved the folder to the next one (this happened often), but the search and browsing of the folders did not give any results. Later, within an hour, several more calls were received with a similar problem.
It is worth noting that about 5 folders in different directories have disappeared. The network storage is configured with the mirroring function. Those. these files were also not found on the second disk. It was decided to disable network storage in order to avoid overwriting.
Next, the disk was removed and connected to a computer running windows, the device was detected and it was proposed to format the disk. Refused. As it turned out, the file system of the disk is ext4. Later, there were attempts to view the files on ubuntu and scanned with r-linux, but the files and folders were not found.
Question to connoisseurs: how can I recover data? what could have happened and what caused the folders to disappear? what steps can be taken?
ps deletion of files and folders by users - we do not exclude (although there are no offended and disadvantaged employees), the total files on the disk are 170 GB, of which 140 GB is displayed, but 30 GB does not show (that is, in fact, this data is still on disk)

Answer 1

well, first you need to look at the logs on your storage
, perhaps the file or disk has crashed and you need to run the fscheck,
well, in general, you need to restore it from the backup

Answer 2

Try these: liberatum.ru/exclusive/ext3-ext4-file-recovery