|You WILL loss data. Its just as question of when!|
At some point in your life you WILL loose data from a disk. Be it physical failure or purely accidental file deletion it WILL happen to you.
The first thing to understand is to how you can mitigate these possibilities.
Techniques and Technology.
If you have data that needs to be held securely then hold this on fit for purpose storage. RAID systems were invented for this very reason. Ranging from the simple mirroring (RAID1) to the most complex node based data servers that can loose entire servers and still maintain data integrity.
It is also vital to ensure that the system is actively monitored and any disk failures or expected disk failures be reported (usually by email) to the appropriate people and disk swapped out to maintain an effective secure system.
Back Up / DR planning
In some cases it is prudent to ensure that there are off site back ups made. This can be either in the form of Cloud Storage, server synchronisation between sites or even the creation of LTO tapes that allow old data to be safely archived away and therefore free up valuable disk space.
Cloud offerings can range from Google Drive through to Amazons Cloud based storage server, and the solution will obviously be based upon your needs and storage capacity needed.
Software Tools Set
In the event that you DO end up with deleted files (the one thing that is difficult to guard against) there are vendors out there that offer un-erase functions on there software. It is however important to understand that if you have deleted files this has to be identified as early as possible to prevent lost data being over written by data being added to the disk after the deletion process.
I have had varying success with these software recover tools, but the few I have come across that appear to very good and not excessively expensive are...
TestDisk - OpenSource and has a great DOS look and feel to it.
There are also companies who you can take your drive to to see if they can recover data from the disk surface, even with damaged enclosures and controllers.
We can help safeguard against most technology based failures but it is the 32% human factor that usually catches us out, but if you have at least put some measures in place than you should stand a better chance of surviving the hell that can be data loss.