It is indeed possible to recover RAID 5 server but it depends on how it was reformatted. If it was reformatted through the operating system (high-level reformat), such as Windows, it is still possible.
The thing is, if the server is reformatted through a RAID controller unit (low-level reformat), it will be impossible because this kind of format will actually overwrite every single data on the drive and thus, erases the original data that was in the server.

Even if several servers fail all at once, it is still likely to recover RAID 5 server, but the condition of the files and registries that can be recovered will rely upon the amount of damage each failed servers had acquired.
There are numerous articles on how to recover such servers on the internet. These articles are very helpful especially if an immediate solution is needed but this is just advisable if the damage is simple. If the loss is more severe, this would not be the best way to recover a failed drive since it is too risky.

In order to successfully recover RAID 5 server, it is better to contact a trusted data recovery company that can lessen the risk of losing all the vital data on the hard drive.

The process of recovery can be properly set-up and maintained by an expert with enough knowledge. These experts can recover important business data or personal files on different kinds of servers with ease since such companies are equipped with experience, knowledge and resources.