What is the most common cause of hard drive failure?

The most common causes are mechanical wear (drives over 3–5 years old), power surges, overheating, and physical drops or impacts. SSDs fail from excessive write cycles or firmware bugs. Regular backups are the best protection — we recommend the 3-2-1 rule: 3 copies of your data, on 2 different types of media, with 1 copy off-site or in the cloud.